NO174211B - Crankcase lubricant for use in automotive engines comprising a major amount of a low phosphorus and zinc lubricating oil and concentrate - Google Patents

Abstract

Lubricants having antiwear, corrosion inhibition and antioxidant performance appropriate to modern oil requirements with reduced or zero amounts of zinc and phosphorous and without the need for large amounts and/or expensive forms of antioxidant comprise 5 to 500 parts per million by weight (ppm) of added copper present in oil-soluble form, one or more added oil-soluble sulphur-containing compounds and a bearing corrosion inhibitor.

Description

The present invention relates to a crankcase lubricant for use in automobile engines comprising a main quantity of a lubricating oil, 5 to 500 ppm by weight of added copper present in oil-soluble form, one or more added oil-soluble sulfur-containing compounds so that the mixture comprises from more than 0.5 to 2.0 weight # of total sulfur and an effective amount of a bearing corrosion inhibitor.

The invention also relates to a concentrate of such a crankcase lubricant.

Today, there is a constant tendency to reduce the amounts of phosphorus in lubricants because of the harmful effects phosphorus has on catalysts that are usually used in catalytic converters that are used for emission control. Phosphorus levels have typically been in the order of 0.1%, but there is an increasing tendency to reduce phosphorus levels to below 0.05 wt-# or to remove phosphorus altogether. However, zinc dialkyldithiophosphates, ZDDP, and other phosphorus-containing additives have frequently been used as anti-wear and/or antioxidant additives and simply reducing or removing such components results in lubricants with poor machine performance.

US-A-2356661 describes lubricating oils containing 50 to 1000 ppm copper as an oil-soluble organic compound such as copper dialkyldithiocarbamates and including phosphorus-containing compounds together with from 0.1 to 0.5% by weight of total sulfur in the oil, the sulfur being provided as oil-soluble organic sulfur compounds such such as thiocarbamates.

US-A-2343756 describes the addition of copper compounds including phosphorus-containing copper complexes in conjunction with sulfur compounds, to lubricating oils. Amounts from 0.1 to 0.5% by weight of sulfur are described, with amounts in excess of 0.5% by weight sulfur being described as potentially harmful. In US-A-2442580, copper (I) thiophosphates are incorporated into lubricant mixtures at relatively high levels, which give high phosphorus levels in the oils.

In US-A-3346493, a wide spectrum of metal-containing polymeric amine-metal reactants are used as detergents in lubricating preparations. In an isolated example, another lubricant part is described containing, inter alia, a copper salt of an acylated nitrogen compound, 0.075% phosphorus as a ZDDP reacted with hexene oxide, and a sulphurised methyl ester of a talloleic acid. Other copper-containing lubricants contain either more phosphorus or no sulphur. US-A-4122033 describes the whole group of transition metal compounds as antioxidant stabilizers in connection with amines, selenides, phosphines or phosphites and can be used in various applications including as additives for lubricants. None of the preceding documents fully describe the pre-formulated lubricant oils that would be suitable to meet the requirements placed on modern lubricants and none specifically targets the reduction of phosphorus levels while simultaneously maintaining performance in terms of anti-wear, anti-oxidation and corrosion inhibition.

EP-A-24146 describes lubricant compositions containing an ashless dispersant and/or a polymer - viscosity index improving dispersant and copper which may be in the form of a dithiocarbamate, but which requires the presence of 0.01 to 0.5% by weight of zinc and from 0, 01 to 0.5% by weight phosphorus. Thiadiazole polysulfides are a possible component.

US-A-4330420 describes oils with reduced phosphorus content (but only to 0.05% P) using mixtures of dialkyldiphenylamine and a sulfurized polyolefin to compensate for the reduction in the amount of ZDDP. There is no description regarding the use of copper or thiadiazole polysulphides.

EP-A-89844 describes reaction products of 4,4'-methylene-bis(2,6-di-t-butylphenol) and tri-sec-C4_12-alkyl orthoborate and their use in lubricants to enable the amount of ZDDP to be reduced to from 0.05 to 0.11 wt% P.

US-A-4490265 describes lubricating oils comprising boron-containing heterocyclic compounds which can be in the form of a metal salt including a copper salt, thiadiazole polysulphides, terephthalic acid and as an oxidation inhibitor either a bis(dithio-benzyl) metal derivative where the metal inter alia can be copper or a sulphur- bridged, bis-hindered phenol. The desirability of reducing or eliminating phosphorus is not disclosed and all examples of lubricants contain 0.05 wt% P.

US-A-4623474 has a similar description.

US-A-4627930 also describes boron-containing heterocyclic compounds which may be in the form of a copper salt and which may be sulphurised. Thiadiazole polysulfides and copper carboxylates are also described. Although the boron-containing heterocyclic compounds are described as phosphorus-free, there is no disclosure for a fully formulated oil containing less than 0.05 wt% P. US-A-4629580 has a similar disclosure. US-A-4629579 discloses boron and metallic boron derivatives for use as extreme pressure, antiwear and friction reducing additives for lubricating oils and preparations including one that does not contain ZDDP, but it is a description of a composition containing little or no phosphorus , but with sulfur and copper.

Lubricant compositions containing low or no amounts of phosphorus but no copper are described in WO-A-8604601, WO-A-8604602 and WO-A-8606092.

The present invention aims to provide lubricants with anti-wear, corrosion-inhibiting and antioxidant effects suitable for modern oil requirements with reduced or no amounts of zinc and phosphorus and without the need for large amounts or expensive forms of antioxidants.

The term "modern oil" as used here in connection with car crankcase oil j refers to an oil that can meet today's requirements for crankcase lubricants in the major industrial countries. High-performance machines including long-term stays between oil changes and higher operating temperatures all contribute to the increased performance of the lubricants used. The present invention relates in particular to automotive lubricants which meet and exceed the requirements for the SF API "Engine Service Category" for service oils and/or the CD requirements for the CD API Engine Service Category for commercial oils (diesel engines), determined jointly by API, SAE and ASTM.

Accordingly, the present invention relates to a crankcase lubricant for use in automobile engines comprising a main quantity of a lubricating oil, 5 to 500 ppm by weight of added copper present in oil-soluble form, one or more added oil-soluble sulfur-containing compounds such that the mixture comprises from more than 0.5 to 2.0 wt% total sulfur and an effective amount of a bearing corrosion inhibitor, and the lubricant is characterized in that the composition contains less than 0.05 wt% phosphorus and substantially no zinc.

As mentioned at the outset, the invention also relates to a concentrate, and this is characterized by the fact that it comprises an oil solution containing: (1) less than 0.1% by weight phosphorus and essentially no zinc; (2) from 1 to 50% by weight of an oil-soluble sulfur-containing compound; (3) from 0.005 to 2 wt* of copper; (4) from 0.1 to 20% by weight of a bearing corrosion inhibitor; and (5) from 0 to 60% by weight of an ashless dispersant and/or from 0 to 40% by weight of a polymer viscosity index improving dispersant.

In particularly preferred embodiments of the invention, the lubricant mixture will also contain one or more ashless dispersants and/or one or more viscosity index improving dispersants and/or one or more overbased additives that act as antacid and antirust agents, such as overbased calcium or magnesium sulfonates or - phenates.

The use of copper enables, according to the invention, that an oil with a low phosphorus content whose performance meets the requirements of modern oils can be achieved economically and with good control of oxidation, and which in a car engine is catalysed by metal accumulated in the oil due to wear or corrosion, as iron is a special oxidation catalyst. At unduly low copper concentrations, the antioxidant effect may be insufficient for certain applications. At unduly high concentrations, the ash level in the oil will be increased and the increasing tendency for bearing corrosion can be observed. The amount of added copper in the mixtures will generally lie within the range 10 to 400 ppm, characteristically 10 to 300, preferably 10 to 200 and most preferably for example 60 to 200 ppm.

The ability of the mixtures according to the invention, containing low amounts of oil-soluble copper compounds and very low or no amounts of phosphorus, to provide sufficient antioxidant and anti-wear performance for the strict requirements of modern engine tests is surprising. Copper is known to act in many situations as an oxidation promoter or catalyst and closely related metals such as cobalt and chromium are not effective lubricant antioxidants. EP-Å-24146 describes the presence of at least 0.01% by weight of each of phosphorus and zinc.

It is also surprising that the copper compound works effectively in mixtures which may contain zinc and other metal compounds such as calcium- or magnesium-based additives which have an inherent pro-oxidant activity. The copper compounds used as antioxidants in the mixture according to the invention can be chosen from among those described in EP-A-24146 as suitable for lubricants, provided that the copper compounds are essentially free of phosphorus.

Thus, copper can be mixed in the oil as the oil-soluble copper salt of a synthetic or natural carboxylic acid. Examples of suitable carboxylic acids C^Q.j^g-f etic acids such as stearic or palmitic acid, unsaturated acids such as oleic acid, branched carboxylic acids such as naphthenic acids with molecular weights of 200 to 500, neodecanoic or 2-ethylhexanoic acid and alkyl- or alkenyl-substituted dicarboxylic acids such as polyalkene-substituted succinic acids , for example octadecenyl, dodecenyl and polyisobutenyl succinic acids.

The copper can be mixed in the oil as oil-soluble copper dithiocarbamates with the general formula (RR'NCSS)nCu, where n is 1 or 2 and R and R' are the same or different C±- i8~ > preferably C8-i^-hydrocarbyl residues which alkyl, alkenyl, aryl, aralkyl, alkaryl and cycloalkyl radicals. Other copper and sulfur-containing compounds such as copper mercaptides, disulfides and thioxanthates are suitable for use according to the invention. Copper sulphonates, -phenates and -acetylacetonates can also be used.

Alternatively, copper can be introduced into the oil in an oil-insoluble form, provided that the copper, in the finished lubricant mixture, is present in the form of an oil-soluble compound. The term "added copper" is intended to exclude copper present in the oil as a result of accumulation of copper in the oil during use, for example by wear or corrosion of copper-containing components.

The lubricant mixtures according to the invention contain an added oil-soluble sulfur compound. A preferred class of such sulfur compounds are dithiocarbamates, preferably of the formula: (RR'NCSS)n M, where R, R' and n are as indicated above and M is an appropriate metal such as molybdenum or, as indicated above, copper or an optionally substituted hydrocarbyl residue. Preferred dithiocarbamates are dialkyl dithiocarbamates, preferably containing 2 to 12 carbon atoms such as diamyl dithiocarbamates.

Sulfur may also be introduced as a mercaptide, particularly mercaptides of aliphatic mercaptans (including copper mercaptides as noted above), sulfurized unsaturated organic compounds including sulfurized olefins (for example, US-A-4119549, US-A-4-4119550, US-A -4191659 and US-A-4147640), sulphurised Diels-Alder adducts (for example US-A-3632566, US-A-3498915 and US-E-27331) and particularly sulphurised unsaturated alcohols and esters as sperm oil substitutes, sulphides including di - and polysulphides, thioethers, thiophenols, thioxanthates (including copper thioxanthates as indicated above), sulphurised esters, thioesters, thioamides, thiazoles such as benzothiazoles and especially mercaptobenzothiazoles and thiadiazoles.

Mineral lubricating oils contain sulphur, while synthetic oils can be sulphur-free so that the amount of sulfur that is added as a sulphur-containing compound varies according to the base material and the sulfur content of other components in the lubricant mixture, most preferably so that a sulfur content of more than 0.5 to 1.0 wt% total sulfur.

The lubricant mixture according to the invention preferably contains from 0.5 to 0.7 and preferably 0.1 to 0.5% by weight of S added as an oil-soluble sulphurous compound, preferably in the form of a sulphurised ester.

The bearing corrosion inhibitor is a corrosion inhibitor that is effective in inhibiting corrosion effects on bearings such as Cu/Pb bearings, where effects such as copper spotting and high weight loss can be taken into account. Such additives have been found to promote anti-wear performance in the oil. Preferred bearing corrosion inhibitors are borates such as B(0R)3, (RO )2B-0-B(0R)2,

(R0B0)3, (R0)2B0R<1>0B(0R)2 and mixtures (where R is a substituted or unsubstituted alkyl, aryl or aralkyl group or where two groups R together form a substituted or unsubstituted alkylene group and R <1> is a substituted or unsubstituted alkylene group) and these substances can, for example, be derived from alcohols such as alkoxyalkanols (both short-chain alkanols and longer-chain alcohols as in US-A-4440656) and polyetheralkanols; mono-, di- and trihydroxyalkanes, for example 2-ethylhexanol, 2-ethylhexane-1,3-diol, butane-1,2-diol, butane-1,3-diol, glycerol and the acyclic polyols according to US-A-2866811; hydroxy esters such as glyceryl monooleate; oxazolines derived, for example, from oleic acid and tris(hydroxymethyl)aminomethane; sulphur-containing alcohols as they can be obtained by reacting epoxides with mercaptans, for example t-dodecylmercaptoethanol; amino alcohols such as alkanolamines, for example triethanolamine and tri-isopropanolamine, hydroxyamines obtained by reacting a primary amine (for example oleylamine) or a secondary amine with ethylene or propylene oxide and the compounds according to TJS-A-4406802. Preferred alcohols are 2-methylpentane-1,3-diol, butane-1,2-diol, butane-1,3-diol and similar 1,2- and 1,3-diols and ethoxyethanol.

In a preferred embodiment, the object of the invention contains from 0.01 to 10 and preferably from 0.1 to 5 wt-10 of a borate ester, in particular an ester of an alkoxyalkanol or a polyetheralkanol, for example a tris(ethoxyethyl)orthoborate ester or a -metaborate ester , or a biborate of a diol such as a butane-1,3-diol.

Alternatively, the bearing corrosion inhibiting compound is a thiadiazole mercaptan and in particular a thiadiazole polysulfide containing from 5 to 50 carbon atoms, a derivative or a polymer thereof. Preferred substances are the 1,3,4-thia-diazole polysulfides as described in US-A-2719125, 2719126 and 3087932. Particularly preferred is the commercially available compound 2,5-bis-(t-octadithio)-1,3,4-thiadiazole as "Amoco 150" or 2,5-bis(nonyldithio)-1,3,4-thiadiazole available as "Amoco 158". Other similar substances which are also suitable as described in US-A-3821236, 3904537, 4097387, 4107059, 4136043, 4188299 and 4193882. Derivatives of thiadiazole mercaptans can be used as esters, condensation products with halogenated carboxylic acids, reaction products with aldehydes and amines, alcohols or mercaptans, amine salts, dithiocarbamates, reaction products with ashless dispersants as for example described in US-A-4140643 and US-A-4136043 and reaction products with sulfur halides and olefins.

These substances are preferably present in an amount from 0.01 to 10% by weight and most preferably from 0.1 to 5.0% by weight of the lubricant mixture.

The lubricant mixtures may comprise small amounts of phosphorus, less than 0.05 and preferably less than 0.01% by weight, and most preferably less than 0.005% by weight phosphorus, but most preferably the lubricant mixtures are substantially free of phosphorus.

In a preferred aspect, the lubricant mixture further comprises: (A) from 1 to 10% by weight of an ashless dispersant mixture which is: an ashless nitrogen or ester containing dispersant mixture which is preferably selected from: (i) oil soluble salts, amides, imides, oxazolines and esters or mixtures thereof, of long-chain hydrocarbon-substituted mono- and dicarboxylic acids or their anhydrides; (ii) long-chain aliphatic hydrocarbons with a polyamine attached directly thereto; and (iii) Mannich condensation products formed by the condensation of a molar proportion of long-chain hydrocarbon-substituted phenol with 1 to 2.5 moles of formaldehyde and 0.5 to 2 moles of polyalkylene polyamine; wherein the long chain hydrocarbon group is a polymer with a C2-5 monoolefin, the polymer having a molecular weight of 700 to 5000; and/or (B) from 0.3 to 10% by weight of a nitrogenous or ester-containing polymeric viscosity index improving dispersant which may contain: (a) polymers consisting of 04.34 unsaturated esters of vinyl alcohol or 03.^9 unsaturated mono- or dicarboxylic acids with unsaturated nitrogenous monomers of 4 to 20 carbon atoms; (b) polymers of C2_20~olefin with& unsaturated C3_^<q> mono- or dicarboxylic acid neutralized with amine, hydroxyamine or alcohols; and (c) polymers of ethylene with a C3_2()-olefin further reacted either by grafting C4_2o unsaturated nitrogen-containing monomers thereon or by grafting an unsaturated acid onto the polymer shell and then reacting the carboxylic acid groups with amine, hydroxyamine or alcohol.

The nitrogenous dispersant additives are those known in the art as dispersants for crankcase oils, for example as described in US-A-3275554, US-A-3565804, US-A-3442808, GB-A-983040 or BE-A -658236.

The most frequently used dispersants are those formed by reacting alkenyl succinic anhydride, for example polyisobutenyl succinic anhydride, and an amine as described in US-A-3202678, 3154560, 3172892, 3024195, 3024237, 3219666, 3216936 and BE-A-662875.

Alternatively, the ashless dispersants may be esters derived from long chain hydrocarbon substituted carboxylic acids and from hydroxy compounds such as monohydroxy and polyhydroxy alcohols or aromatic compounds such as phenols and naphthols as prepared as, for example, in US-A-3522179.

Hydroxyamines which can be reacted with any of the aforementioned long chain hydrocarbon substituted carboxylic acids to form the dispersants include 2-amino-1-butanol, 2-amino-2-methyl-1-propanol, p-(g-hydroxyethyl)-aniline, 2-amino-1-propanol, 3-amino-1-propanol, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, N-(p<- >hydroxy-propyl)-N'-(3-aminoethyl)-piperazine, tris(hydroxy-methyl)aminomethane (also known as trismethylolaminomethane), 2-amino-l-butanol, ethanolamine, p<->(g< ->hydroxyethoxy)ethylamine, and the like. Mixtures of these or corresponding amines can also be used.

Preferred dispersants are those derived from polyisobutenylsuccinic anhydride and polyethyleneamines, for example tetraethylenepentamine, polyoxyethylene and polyoxypropylamines, for example polyoxypropylenediamine, trismethylolaminomethane and pentaerythritol and combinations thereof. A particularly preferred dispersant combination is a combination of (A) polyisobutenylsuccinic anhydride with (B) a hydroxy compound, for example pentaerythritol, (C) a polyoxyalkylene polyamine, for example polyoxypropylenediamine and (D) a polyalkylene polyamine, for example polyethylenediamine and tetraethylenepentamine using 0.01 to 4 equivalents of (B) and (D) and 0.01 to 2 equivalents (C) per equivalent (A) as described in US-A-3894763. Another preferred dispersant combination involves the combination of (A) polyisobutenylsuccinic anhydride with (B) a polyalkylene polyamine, such as tetraethylenepentamine, and (C) a polyhydroxy alcohol or a polyhydroxy-substituted aliphatic primary amine, such as pentaerythritol or trismethylolaminomethane as described in US-A -3632511.

Dispersants of the alkenyl succinic acid polyamine type can be further modified with a boron compound such as boron oxide, boron halides, boronic acids and esters of boronic acids in an amount that gives 0.1 to 10 atomic parts of boron per mol of acylated nitrogen compound as generally described in US-A-3087936 and 3254025. Mixtures of dispersing agents can also be used as those described in US-A-4113639.

The oils may contain from 1.0 to 10 and preferably from 2.0 to 7.0% by weight of these dispersants.

The dispersing ability can be provided by means of 0.3 to 10% of a polymeric viscosity index improving dispersant, for example copolymers of alkyl methacrylates with N-vinylpyrrolidone or dimethylaminoalkyl methacrylate, alkyl fumarate-vinyl acetate N-vinylpyrrolidine copolymers, post-grafted interpolymers of ethylene-propylene with an active monomer which maleic anhydride which can be further reacted with an alcohol or an alkylene polyamine, as described in US-A-4149984; or styrene/maleic anhydride polymers which are subsequently reacted with alcohols and amines, ethoxylated derivatives of acrylate polymers such as in US-A-3702300.

Magnesium- and/or calcium-containing additives are frequently used in lubricant mixtures either alone or in combination with other alkali metal or alkaline earth metal additives such as those containing sodium. These can be present, for example, as metal salts of sulphonic acids, alkylphenols, sulphurised alkylphenols, alkylsalicylates, naphthenates and other oil-soluble mono- and di-carboxylic acids.

Strongly basic alkaline earth metal alkyl sulfonates are generally known, for example, from US-A-3150088 and 3150089. For the purposes of the invention, a preferred alkaline earth metal sulfonate is magnesium alkylaromatic sulfonate with a total base number, TBN, measured according to ASTM D2896, from 300 to 400. Polyvalent metal alkyl salicylate- and naphthenate substances can also be incorporated in the same way as methylene- and sulfur-bridged substances which can be easily derived from alkyl-substituted salicylic or naphthenic acids or mixtures of such with alkyl-substituted phenols. Basic sulphurised salicylates and a method for their preparation are described in US-A-3595791.

The sulphurised metal phenates can be regarded as the "metal salt of a phenol sulphide" which thus refers to a metal salt, regardless of neutrality or base, of a compound characterized by the general formula:

where x = 1 or 2 and n = 0, 1 or 2, or a polymeric form of such a compound where R is an alkyl radical, n and x are both integers from 1 to 4 and the average number of carbon atoms in all the R groups is at least approx. 9 to ensure adequate solubility in oil. The individual R groups may each contain from 5 to 40 and preferably 8 to 20 carbon atoms. The metal salt is prepared by reacting an alkylphenol sulfide with a sufficient amount of metal-containing material to give the desired alkalinity to the sulfurized metal phenate.

The sulfurized alkylphenol is converted by reaction with a metal-containing material containing oxides, hydroxides and complexes in an amount sufficient to neutralize the phenol, and, if desired, to overbase the product to a desired alkalinity by methods known per se. A process with the neutralization using a solution of metal in a glycol ether is preferred.

Magnesium- and calcium-containing additives as described above, although they may be beneficial in other respects, may increase the tendency of the lubricant to oxidize. This is particularly the case in the case of the strongly basic sulphonates.

According to a preferred embodiment of the invention, a crankcase lubricant mixture is therefore provided which also contains from 2 to 8000 ppm calcium and/or magnesium.

Magnesium and/or calcium are generally present as basic or neutral detergents such as sulfonates and phenates, and preferred additives are basic magnesium or calcium sulfonates. Preferably, the oils contain from 500 to 5000 ppm calcium and/or magnesium from such additives.

These mixtures according to the invention can, as an alternative or in addition, contain other corresponding metal-containing detergent additives, for example those containing barium, sodium, potassium or lithium.

The lubricating oils used in the lubricant mixtures can be mineral lubricating oils or a synthetic lubricating oil or a mixture thereof. Suitable synthetic oils include diester oils such as di(2-ethylhexyl)sebacate, azelate and adipate; complex ester oils such as those formed from dicarboxylic acids, glycols and either monobasic acids or monohydroxy alcohols; silicone oils; sulphide esters; organic carbonates; hydrocarbon oils and other synthetic oils well known in the art. The invention is particularly useful when it comes to mineral lubricating oils and has the further advantage that it can also allow the use of basic raw material oils which have poorer antioxidant properties than those usually used.

The lubricant mixtures according to the invention can and will usually contain other traditional lubricant additives provided that they are essentially zinc- and phosphorus-free, for example rust inhibitors such as oleic acid and its derivatives such as N-oleylsarcosine, and oleic acid dimers and trimers, lecithin, sorbitan monooleate, dodecyl succinic anhydride or ethoxylated alkylphenols ; pour point depressants such as copolymers of vinyl acetate with fumaric acid esters of coconut oil alcohols; and viscosity index improvers such as olefin copolymers or polymethacrylates.

In copper-free oils, other antioxidants in addition to zinc dialkyldithiophosphate are sometimes necessary to improve the oxidative stability of the oil. These supplementary antioxidants are especially incorporated when the basic raw material has poor oxidative stability; characteristically, additional antioxidant is added to the oil in amounts from 0.1 to 1.5% by weight. The supplementary antioxidants used include phenols, hindered phenols, bisphenols and sulphurised phenols, catechol, alkylated catechols and sulphurised alkylcatechols, diphenylamine and alkyldiphenylamines as well as phenyl-l-naphthylamine and alkylated derivatives thereof.

The incorporation of small amounts of copper generally removes the need for these supplementary antioxidants. However, it will still be within the scope of the present invention that an additional antioxidant is incorporated especially for oils that work under particularly severe conditions where the presence of such supplementary antioxidants can be beneficial, provided that significant amounts of phosphorus are not thereby introduced.

Additives for lubricating oils are generally supplied as concentrates in oils for incorporation into the mass of lubricant. The present invention therefore provides concentrates comprising an oil solution containing: (1) less than 0.1 wt% phosphorus and less than 0.1 wt% zinc; (2) from 1 to 50% by weight of an oil-soluble sulfur-containing compound;

(3) from 0.005 to 2 wt% copper; and

(4) from 0.1 to 20% by weight of a bearing corrosion inhibitor;

and optionally a dispersant selected from:

(a) 0 to 60, for example 10 to 60% by weight of an ashless

dispersant compound,

(b) 0 to 40, for example 3 to 40% of a polymeric viscosity index improving dispersant, although it is customary to add each viscosity index improving agent separately.

The concentrate may also contain other additives such as the detergents and viscosity index improving agents described earlier. A particularly preferred concentrate also contains a magnesium- and/or calcium-containing additive and the invention therefore provides a concentrate which further comprises from 0.01 to 8% by weight of calcium and/or magnesium.

The following examples are given to illustrate the invention.

Comparative Examples I-VI and Examples 1 and 2

In the following comparative examples and examples according to the invention, formulations are prepared with combinations and quantities of additives as indicated in table 1, the remainder being a diluting oil suitable for lubricant preparations and comprising 0.3% by weight of sulphur. The additives used are as follows: A is a dispersing viscosity-improving additive comprising an oil solution containing 21% of a multifunctional ethylene-propylene copolymer and containing 0.29% by weight N;

B is an ashless dispersant comprising a 50% by weight oil solution of a borated polyisobutenyl succinimide with a polyisobutenyl residue having a molecular weight of approx. 950 and containing 1.6 wt% N and 0.35 wt% B;

C is an oil solution of an overbased magnesium sulfonate with a TBN of 400 and a magnesium content of 9.2% by weight and a sulfur content of 1.7% by weight;

D is an oil solution of an overbased calcium sulfonate with a TBN of 300 and a calcium content of 11.9% by weight and a sulfur content of 1.9% by weight;

E is an oil solution of copper oleate containing 4% by weight of copper;

F is a 30% by weight solution in oil of a hindered methylene-bis-phenol antioxidant;

G is an alkylated diphenylamine antioxidant, commercially available as "Irganox L-57";

H is a 50% by weight oil solution of a zinc diamyl dithiocarbamate containing 6% by weight zinc and 12% by weight sulfur;

J is an orthoborate ester prepared from ethoxyethanol and comprising 5 to 6% by weight boron;

K is 2,5-t>is(nonyldithiol)-1,3,4-thiadiazole, commercially available as "Amoco 158" and containing 33% by weight of sulfur;

L is an oil solution containing 12% by weight of molybdenum as octoate; and

M is a sulfurized ester sperm oil substitute, commercially available as "Emery 9844" and comprising 11.5% by weight sulfur.

The suggested formulations were tested in the following standard tests: "Seq. IIID" engine test according to "ASTM STP 315M Part II" where maximum and average cam plus lifter wear is measured. A successful test according to this is achieved with a maximum wear of 0.02 cm or better and an average wear of 0.01 cm or better;

The kinematic viscosity increase in Seq. IIID was measured at 40°C as a percentage increase over 64 hours. A successful sample is obtained in this examination by achieving a viscosity increase during 64 hours of no more than 375%.

"CRC-L-38-Screener" engine test based on "ASTM STP 509A PE IV" where the bearing weight loss, BWL, is measured. A successful sample here is achieved with a BWL value of no more than 40 mg.

The results obtained are shown in table 2. These results show that the present invention provides a surprising advantage with regard to lubricants that have excellent antioxidant, antiwear and bearing corrosion inhibiting properties with a virtually total absence of phosphorus and zinc. Comparative Examples I, II and III show that in the absence of a bearing corrosion inhibitor, performance was inadequate. Comparative Example IV shows that the addition of a molybdenum additive did not improve wear performance. Comparative Example V shows that in the absence of copper antioxidant the performance was insufficient even with conventional amounts of other known oxidizers.

The examples given here show that the performance of the formulations as described above is not just a summary of the performance of the individual additives, but gives a surprising improvement in anti-wear, antioxidant and bearing corrosion performance, while at the same time achieving phosphorus levels far below what is commercially used in conventional oils. Concentrates - Typical concentrations for providing the above listed formulations.

The concentrates may also contain some diluting oil to improve processing, i.e. reduce viscosity.

Claims (15)

1. Crankcase lubricant for use in automobile engines comprising a major amount of a lubricating oil, 5 to 500 ppm by weight of added copper present in oil-soluble form, one or more added oil-soluble sulfur-containing compounds such that the composition comprises from more than 0.5 to 2.0% by weight in total sulfur and an effective amount of a bearing corrosion inhibitor, characterized in that the mixture contains less than 0.05% by weight phosphorus and substantially no zinc. 2. Mixture according to claim 1, characterized in that the amount of copper in the mixture is from 10 to 400, preferably 10 to 200 and most preferably from 60 to 200 ppm by weight. 3. Mixture according to claims 1 and 2, characterized in that copper is present in the oil as the copper salt of a C^q to C^g fatty acid, an unsaturated carboxylic acid, a naphthenic acid with a molecular weight from 200 to 500 or an alkyl- or alkenyl-substituted dicarboxylic acid, oil-soluble copper dithiocarbamates of the general formula (RR'NCSS)nCu, where n is 1 or 2 and R and R' are the same or different hydrocarbyl residues containing 1 to 18 carbon atoms, a copper sulfonate, a copper phenate or a copper acetylacetonate. 4. A mixture according to any one of the preceding claims, characterized in that the oil-soluble sulfur compound is a dithiocarbamate of the formula: (RR'NCSS)nM, where R, R' and n are as stated in claim 5 and M is a suitable metal, or a mercaptide, a sulphurised unsaturated organic compound, a sulphide, a thioether, a thiophenol, a thioxanthate, a sulphurised ester, a thioester, a thioamide, a thiazole or a thiadiazole, preferably a dialkyldithiocarbamate containing 2 to 12 carbon atoms. 5 . Mixture according to any one of the preceding claims, characterized in that it contains from more than 0.5 and up to 1.0% by weight of total sulfur including from 0.1 to 0.5% by weight of sulfur as an added oil-soluble sulfur-containing compound . 6. Mixture according to claim 4, characterized in that it contains from 0.5 to 3.0% by weight of sulfurized ester. 7. Mixture according to any one of the preceding claims, characterized in that the bearing corrosion inhibitor comprises one or more borate esters with the formulas: B(OR)3 or (RO)2B-0-B(OR)2, (R0B0)3 or (R02) B0R10B(0R)2 (where R is substituted or unsubstituted alkyl, aryl or aralkyl or two groups R together in the form of a substituted or unsubstituted alkylene group and R<1> is a substituted or unsubstituted alkylene group) and/or a thiadiazole polysulfide containing from 5 to 50 carbon atoms, a derivative or a polymer thereof. 8. Mixture according to claim 7, characterized in that it contains from 0.01 to 10% by weight of a borate ester, preferably a tris(ethoxyethyl)orthoborate ester or a biborate of butane-1,3-diol. 9 . Mixture according to claim 7, characterized in that it contains from 0.01 to 10% by weight of 2,5-bis(t-nonyl-dithio)-1,3,4-thiadiazole. 10. Mixture according to any one of the preceding claims, characterized in that it contains less than 0.005% by weight of phosphorus, but is preferably essentially phosphorus-free. 11. Mixture according to any one of the preceding claims, characterized in that it further comprises: (A) from 1 to 10% by weight of an ashless dispersant and/or (B) from 0.3 to 10% by weight of a nitrogen - or ester-containing polymeric viscosity index-improving dispersant. 12. Mixture according to any one of the preceding claims, characterized in that it comprises from 2 to 8000, preferably from 500 to 5000 ppm calcium and/or magnesium, preferably as a basic calcium and/or magnesium sulphonate. 13. Mixture according to any one of the preceding claims, characterized in that it further comprises one or more rust inhibitors, pour point depressants, further antioxidants or viscosity index improving agents. 14 . Concentrate, characterized in that it comprises an oil solution containing: (1) less than 0.1% by weight phosphorus and substantially no zinc; (2) from 1 to 50% by weight of an oil-soluble sulfur-containing compound; (3) from 0.005 to 2 wt% copper; (4) from 0.1 to 20% by weight of a bearing corrosion inhibitor; and (5) from 0 to 60% by weight of an ashless dispersant and/or from 0 to 40% by weight of a polymer viscosity index improving dispersant. 15 . Concentrate according to claim 14, characterized in that it further comprises from 0.01 to 8% by weight calcium and/or magnesium.