US2375222A

US2375222A - Aviation lubricating oil

Info

Publication number: US2375222A
Application number: US502706A
Authority: US
Inventors: Jr John R Griffin; Paul R Van Ess
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1943-09-15
Filing date: 1943-09-15
Publication date: 1945-05-08
Anticipated expiration: 1962-05-08
Also published as: NL66836C; DE865343C; USRE23229E; GB594960A; GB681091A; US2410652A

Description

Patented May 8,

avm'riou Lnnnrcarmc on.

No Drawing. Application September 1 .5, 19413,

Serial No. 502,106

15 Claims. (c1. 252-23) This invention relates to addition agents which contribute valuable properties to lubricating oil. It also relates to improved lubricating compositionscontaining the herein described additives.

It is known that a substantially non-corrosive, undoped, lubricating oil generally'becomes progressively corrosive under ordinary conditions of engine use. This tendency is increased or accelerated. for instance, by an elevation of temperature, by traces of dissolved copper, by degradation products formed in the oil, and by other factors. It is a common practice to add a detergent to a lubricating oil in order to assist in the removal of soot or sludge which is formed in the engine operation and thus to help keep the bearing surfaces clear. However, normally such detergents simultaneously contribute to or increase the corrosiveness of the lubricating oil. Similarly, additives employed for other purposes may, also prove corrosive. This result is particularly unfortunate, if uncorrected, when ittions may preferentially remove the copper.-

Again, the effect at high temperatures modern bearings, of sulfur derived from certain of its compounds or even found free in the oil or fuel, may be very serious. Thus, in hot countries a crankcase temperature of 250-300 F. may

occur, with the corresponding bearing temperatures going up to 325 F. or 350 F. Under these conditions sulfur can produce hard, brittle, black deposits on copper-lead or silver bearings. Such deposits may adhere and reduce the bearing clearance or they may break up and gouge out the bearing, in either event resulting in bear-- ing failure.

The problem 'of engine deposits is particularly acute in aviatio and similar engines, in which the high temperatures developed in the cylinders tend to act upon lubricating oils to cause the deposition of resinous and varnish-like products on the pistons and elsewhere and to produce lacquer-like coatings and carbonaceous materials, which in time tend to cause ring and valve sticking and interfere with engine operation. High piston temperatures found especially in aviation engine promote t formation of deposits which, in turn, aggravate the situation by reducing the heat transfer. Furthermore, fuel residues from incomplete combustion of fuel contribute to the deposition of lacquer-like and carbonaceous materials in the engine. Solution of the problem is additionally complicated by rigid government specifications for aviation lubricating oil which restrict the incorporation of any additives, such as metallic salts, which would leave a non-volatile ash upon combustion. At the most, thetotal ash content should not exceed about 0.2% (determined as sulfate).

Accordingly, it is an object of this invention to provide lubricating oil compositions which have improved properties in one or more of the following qualities: high temperature detergency, decreased piston ring sticking, wear reduction, corrosion resistance; stability in presence of copper or crankcase catalyst, oxidation stability, and the like. Another purpose is to produce a superior heavy duty lubricant particularly suit able for use in aircraft and other internal combustion engines operating at relatively high cylinder temperatures. Other objects will be apparent from the following description.

It has now been found that such lubricating problems may be overcome to a notable extent by the incorporation in a lubricating oil of two additives. The first of these additives is an oil-miscible metal salt of the condensation product of a low molecular weight aldehyde with a hydrocarbon substituted phenol. The second additive is an organic sulfur-containing antioxidant (as will be more fully described hereinafter).

The first additive is more fully described by the following. It is initially a condensation product of a phenol with an aldehyde. The phenol must have an available ortho position, i. e. an unsubstituted p 'ition ortho to the hydroxyl radical, and also such substituent groups, preferably in the 4 or 2,4 positions, as will promote oil solubility. For example, alkyl, cycloalkyl or aryl groups, such as butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, lauryl, stearyl, oleyl, cyclohexyl, methylcyclohexyl, ethylcyclohexyl, dimethylcyclohexyl, propylcyclohexyl, trimethylcyclohexyl, dicyclohexyl, methylated dicyclohexyl, benzyl, ethylphenyl, etc., are effective. The aromatic nucleus as well as attached hydrocarbon radicals may also contain chlorine. The aromatic nucleus may be monoor di-cyclic, resulting in such nuclei as naphthalene, tetraline, diphenyl, etc.

A. lower molecular weight aldehyde, preferably formaldehyde or acetaldehyde, iscondensed with the phenol at the ortho position by ways known to the art, for example by heating with acid or basic catalyst, whereby a resinous condensation product is obtained. Depending upon starting materials and condensation conditions, the products vary in appearance from viscous liquids to more or less brittle solids which may or may not be crystallized. A number of such resinous condensation products are commercially available, and since their methods of manufacture are generally known, further details regarding such manufacture will not be recounted here.

The phenolic resin is in turn converted to the metallic salt, for example by heating with hydrated lime to produce the calcium salt. In general, the alkaline earth metals are preferred to form the salt, although other polyvalent metals such as Cu, Zn, Al, Pb, Fe, Ni, Co, Mn, Cr and Sn may be employed.

The resultant metal phenates may be difiicultly soluble, in oil. However, they may be incorporated in oil by the procedure described by Corthen be diluted with further oil'to give the desired salt concentration when needed. On the other hand, the salt may often be incorporated in alubricating oil, without preparing an intermediate concentrate, by simply adding the desired concentration of the salt to the oil at an elevated temperature with agitation.

- The amounts of the phenol-aldehyde resin salt which may be added to aviation and similar high temperature lubricating oils must not exceed about 0.2% ash, because ash in these lubricating oils eventually accumulates in the combustion chamber of the aviation engine by leaking past the piston and piston rings, or else leaking into the super-charger (with which most aviation engines are now equipped) whence it returns with the air to the combustion chamber. About of the oil lost in aviation engines is normally by way of the super-charger.

It has been stated that phenol-aldehyde resin salts act as anti-oxidants "in lubricating oils. However, we found that under the high temperature conditions in aviation engines and in the amounts of ash contents of 0.2% or less, such is not the case. Only when added in much larger amounts, 1. e. of ash contents of 0.3% or higher, do these salts show anti-oxidant properties in aviation lubricants under aviation lubricating, conditions.

As a result of their lack of anti-oxidant properties, aviation lubricating oils containing these salts in the perimissible amounts are not only oxidation unstable, but may also be corrosive, and to overcome these detrimental efiects. we add a second addition agent to lubricating oil as described below.

The second additive is an oil-soluble, relatively stable, organic sulfur antioxidant, free from corrosive sulfur, having preferably not more than a single polar radical (if any) other than a sulfur containing radical. Sulfurantioxidants should contain at least about 7 carbon atoms, and preferably 10 or more, and are characterized by containing the sulfur, in a form so that it is somewhat reactive, but not too reactive, with heavy metals such as copper, lead, iron, etc., at temperatures between, say, C. and 300 C.

.It is known that sulfur in the form of sulfides (RSR', where R and R are the same or different hydrocarbon radicals), thiophanes, thiophenes, sulfoxides, sulfones, sulfonates, etc., is too inert for antioxidant purposes. Antioxidant sulfur may be in the form of mercaptans, as in decyl mercaptans, dodecyl mercaptans, cetyi mercaptans, oleyl mercaptans, stearyl mercantans, butyl or other higher alkyl thiophenes, thionaphthols, alkyl thionaphthols, etc.; or of disulfides (RSSR, as in diamyl disulfide and higher dialkyl disulfides, e. g. wax disulfides, diphenyl disulfides, dibenzyl disulfide, dinaphthyl disulfides, etc); or of sulfur compounds formed by attaching sulfur to an olefinic double bond (as by reacting sulfur with olefins at temperatures of about 150 C. to 300 C.) which compounds are believed to contain the structure (sulfur in epithio linkage).

Many sulfur compounds naturally occurring in petroleum oils are useful antioxidants, provided they have the necessary reactivity. These have seen described in detail in the copending appliaction being restricted in most instances to lower :ation, Serial No. 496,678, filed July 28, 1943, by

iistillates with clay or other refining agents, or

n the polymerization of normally gaseous olefins ;o produce gasoline or the like (e. g. sulfurized nethyl pentadiene polymer); sulfurized esters of msaturated fatty acids with monohydrie alco- 1o1s, as methyl, ethyl, propyl, etc., oleate, or inoleate; sulfurized sperm oil; sulfurized jojoba )il; etc. Less desirable are vsulfurized fatty oils vhich contain three ester radicals and hence tend cause excessive carbon formation under the iigh temperature conditions of aviation engines Higher polysulfides, such as compounds of the ;ype RSnR' where n is a whole number of 3 or iigher, as -well as other sulfur compounds con- .aining corrosive sulfur, are so reactive that they tttack bearing metals, causing a build-up of a .hick sulfide film which eventually breaks off, eaving behind a severely damaged bearing surace.

Effective amounts of the sulfur containing addiives in an aviation lubricating oil are in the order if 0.025% to 0.30% by weight of added sulfur, a1: hough quantities of between 0.05% and 0.1% are lsually sufllcient. Amounts of the metallic |henate between about 0.4% and 0.2% sulfate ash nay be'employed. It will be seen that the small .mounts of additives suflicient to accomplish the iresent purpose are much less than would be re- [uired to alter the viscosity omposition.

It has been found that the combination of the .ldehyde-phenol condensate metal salt and a sulur antioxidant in aviation lubricating oil has ad- 'antages which could not be obtained by any ther combination of additives. These advanages are, in particular, non-corrosiveness, deterency at high operating temperatures (with reulting engine cleanliness and prevention of ring ticking), prevention-or at least reduction-of lard carbon formation and a hitherto unachieved eduction in wear, especially of piston rings.

To appreciate these advantages, it may be well 0 consider a few of the difliculties which confront he producer of improved aviation lubricants. It

of the lubricatingwell known that ring sticking is one of themost I requent causes of damage to aviation engines hich are lubricated by straight mineral lubriating oils. While ring sticking can be overcome a a certain extent by the use of tapered piston ings, this advantage is gained at the expense f .a. new difliculty, namely, ring feathering. Ring ticking in aviation engines is a high tempera- .ll'e detergency problem, while ring'feathering L a wear problem.

Many detergents have been proposed to overome ring sticking. However, with few excepons they fail to function at the high temperan'es of aviation engine operation, their beneficial temperatures such as occur in Diesel engines and automotive engines. It has been discovered, however, that the aldehyde-phenol condensate salts of this invention exert an unexpected detergency at high temperatures, but not at low temperatures. At the same time, these salts somewhat reduce engine wear and also cause a very pronounced softening of hard carbon normally formed.

Now as a result of the presence of a metal containing detergent, corrosiveness of the oil increases. It has been said that antioxidants overcome corrosiveness induced by detergents. ever, this does not always appear to be true. For example, the aldehyde-phenol condensate salts are known to exhibit antioxidant action at low temperature and therefore might be expected to inhibit this corrosiveness. However, this was found not to be the case when employing 0.2% (sulfate ash) of the additive. Certain other antioxidants, like secondary aromatic amines, e. g. diphenylamine, etc., do to some extent in hibitthis corrosiveness, but have the disadvantage of causing at least a partial'loss of the carbon softening properties. Moreover, these inhibitors, like the ordinary phenolic inhibitors, such as the 2,6-di-tertiary-butyl-4-methyl-phenol, or the amino phenols as para-benzylaminophenol, fail to have any effect on the wear properties.

The sulfurized antioxidants described earlier, however, have a very. peculiar effect on the aviation oil in combination with the aldehyde-phenol condensate salt. Not only d they do away with the corrosiveness of the oil, but they further greatly enhance the wear reduction and in some instances furtherreduce hard carbon formation. The additive effect in the matter of wear reduc tion in itself is believed to be unusual. As a rule, two wear reducing agents do not cooperate unless they meet certain conditions indicated below, and

on the contrary merely compete for the surface,.

the more strongly absorbed compound displacing the other. Therefore, in so far as wear reduction The mechanism of boundary lubrication, Proceedings of 71118 Royal Society of London, Serial A,,No. 968, vol. 177, pp. 90 to 118, December, 1940, and in the Proceedings of the Special Summer Conference on Friction and Surface Finish of Massachusetts Institute of Technology, Cambridge, Mass., June 5, 6 and '7, 1940, p. 112, has it been known that two or more wear reducing agents cooperate. However neither of the two additives of this invention is a chemical polishing agent, although some of the sulfur antioxidants may fall into the class of wedging compounds.

Due to" this strong wear reducing effect combined with the detergency, the present oil will ameliorate high temperaturedifiiculties whetherdue to ring sticking-or ring feathering, so that it may be employed advantageously with either the straight or tapered type of piston ring.

' In military aircraft engine service in which piston ring belt lubrication is a primary problem,

, this lubricating oil composition, by its reduction of ring sticking and wear, offers a unique and- The preparation of a typical aldehyde-phenol condensate salt is illustrated by reference to the use of calcium salts of methylene bis p-isooctylphenol. This compound was prepared by condensing phenol and di-isobutylene to yield an (principally para) isooctylphenol. This was then condensed with formaldehyde to yield the resinous condensation product containing about five molecules of isooctylphenol per molecule of resin, .1

but which for convenience is called methylene bis p-isooctylphenol. The condensate was converted to calcium salt by reaction with lime as follows: About equal weights of resin and CaO were ground together to a fine powder. Water was added and the mixture heated on a steam bath in an open vessel. A vigorous reaction took place involving hydration of CaO and formation of the phenate salt. benzene and filtered from. excess Ca(OI-I) 2. The bulk of the benzene was removed by distillation at atmospheric pressure; the remainder of the solvent was stripped under reduced pressure.

The resulting residue, a glassy amorphous solid, was then ground to a yellow-green powder. The

sulfate ash values of different batches varied from about 20% to 22%.

Our aviation oil additives were tested alone and together in the multiple four-ball machine similar in principle to th Boerlage apparatus described in the magazine, Engineering, volume 136, July 14, 1933. This apparatus comprises four steel balls arranged in pyramid formation. The top ball is rotated by spindles against the three bottom ballswhich are clamped in a stationary ball holder. The balls are immersed in the oil to be tested. Tests were run for two hours at 700 R. P. M. under various loads and at a controlled temperature of 130 C. The diameters of the The salt was taken up in warm Results were as follows:

TABLE I WEAR EVALUATION IN THE MULTIPLE FOUR-BALL MACHINE [A refined, undopcd, commercial aviation lubricating oil, -125 S. U. at 210 F. was employed] Scar diameter (mm.) at the No. of following Additive deterloads, kg.

minations 1 None 4 .29 .70 .75 2 Calcium salt of methylene bis p-isooctylphenol (sulfate ash=0.l%) 2 l2 35 73 3 Calcium salt of methylene bis p-isooctylphenol (sulfate ash=0.3)%) 2 l1 l9 24 4 Calcium salt of methylene bis p-isooctylphenol+barium dialkyl dithiophosphate :1 ratio, total sulfate ash=0.1%) 2 14 47 77 5 Calcium salt. of methylene bis p-isooctylphenol+calcium petroleum sulionate (4:1 ratio, total sulfate ash=0.l%) 2 l1 34 73 6 Calcium salt of methylene bis p-isooctylphenol+suliurized wax olefin (sulfate ash=0. 1%, added sulfur= 0.1%) 2 .13 .21 .28 7 Barium dialkyl dithiophosphate (B280. ash=0.22%) 2 24 .30 .34

The doped and undoped oils were then further tested by a test known as the thrustbearing corrosion test (described in the National Petroleum News, September 17, 1941, pp. 12294-296) which is carried out as follows: A hardened steel disc is made to rotate for 20 hours under constant pressure against three flat copper-lead bearings. The bearing assembly rests in a steel cup filled with the oil to be tested, and the temperature of the oil is maintained at a predetermined figure by thermostatic control. The bearings are weighed before and after the test, the difference in weight representing the loss sustained durin the test.

TABLE II 'Ins'rs IN Tr-musr BEARING CORROSION MACHINE [Fixed conditions: Cu-Pb bearings,

20 hours duration, p. s. i. Thrust, 2400 R. I. M. A

refined, undoped, commercial aviation lubricating oil, 115-125 S. U. at 210 F. was employed] Bearing weight loss in Estimated Additive appro rim ate (Delta s=0.1% for each additive) ggggg 0. o. c. c. o. empm 0'. None .I I. 0. l 0. 3 26. 8 180. Calcium salt of methylene bis p-isooctylphenol (sulfate 0.3 0. 7 49. 0 47. 7 155' &Sh=0-1%) 0.1 0.6 17.8 v o. 2+sulfurized wax olefin 0.3 g. g 0. 3 --0. 4 Above 160. N0. 2+sulfurized sperm oil 0.6 01 2 o. 1 Above 110. No. 2-1-dibenzyl disulfide 0. 8 4. 8 31. 4 155. No. 2+dodeeyl disulfide 0. 0 7. 5 29. 8 Below l5 -L No. 2+suli'urized methyl pentadiene polym 8.8 0. 5 0.1 Above 170.

wear scars worn on the three balls forming the base of the pyramid were then measured, and the average taken as the true indication of wear.

The oxidation stability of lubricating oil containing the present additives was also determined in the presence of copper and crankcase catalysts as follows:

TABLE III STABILITY AND Snuncme DETERMINATIONS I [A refined, undoped, commercial aviation lubricating oil, 115-125 S. U. at 210 F. was employed. Temperature, 150 C nk Catalyst: 1 cm. Cu./g. oil O Addmws 1800 1 N t a] s h 1 U m eu r apom casopenoxygen 0. tion No. tanc gg 1800 g time increase increase insoluble Hours Per cent Per cent Hours one 9. 4 3. 7 1B. 5 0. 04 @1- f 2 Calciumsaltoimethylenebisp-isooctylpbenol(sulfate ash =0.1%) 8. s 4. 0 16.0 t 3 Preoeding+sulfurized wax olefin (added su1fur=0.1%) 65. 4 3. 2 17. 6 o

' All oxidation products corrected to 1800 ml. oxygen absorbed/100 oil, assuming amount of product is proportional to oxygen absorbed.

t Sediment centrifuged from used oil drained from auto craukcasw {see 35 Ind. Eng. Chem. 681 (1943)).

3 Oxidation curve shows induction period.

Efiectiveness of a lubricant containing the presnt combination of lubricating oil additives in ctual engine tests as well as comparison with nine other blends may be seen from the follow- Ilg data: T IV trmnme CORROSIVENESS AND USED OIL PROPERTIES Lawson 1 cylinder liquid cooled engine peed 1700 R.P.M.

MEP 55 psi.

. 1.6 H.P. 1 kw.)

Aviation base-stock 40 hours [A refined, undoped, commercial aviation lubricating oil, 115-125 S. U. at 210 F. was employed] Cu-Pb Sap. No. Neut. Concentration bearing 01] con- MgKOH MgKOH Isopent. Chlor. Additive in percent weight sumption, ins.,

sulfate ash loss, cc./hr. percent percent mg./cm. g g

0119 1.3 21.1 0.8 0.01 0.01 aicium salt of methylene bis p-isooctylphenol 8; alcium salt ofmethylene bis p-is00ctylphenol+sul- 0.10:1: .1. 1:0 313 416 014 0.06 0:08 turized wax olefin. 0.1017? w. added- 0.9 4.9 4.3 0.4 0. 05 0. 04

su ur.

TABLE V Prsron RING WEAR CFR 1 cyl. variable comp. ratio Diesel- 8 ed 900 R, P. M. B EP 60p. s. i. Air intake temp 50 C. refined, undoped, commercial aviation lubricating oil, 115-125 S. U. at 210 F. was employed] Tenpera- 'Iiotal ures p s on Additive Test ring Per cent.

length weight wear I Jacket Oil loss 5 Hours C. 0. G'mme callciumbsalt ti)! metltiy ene 18 psoocty phenol (sulfate ash= 40 0.1%) 52 60 93 0. 0845 70 7 Calcium salt of methylene bis p-isooctylphenol+sulfurized wax olefin (added sulfur=0.1%) 52 60 93 0.0662 1 49 1 Per cent wear= total piston ring weight loss ressed as er cent that with undoped oil. exp p 1 Average.

TABLE VI GENERAL PERFORMANCE Pnopna'rras Speed 2350 R. P M IME 225 p. s 1 Cylinder temperature:

Head F. Base" 325 F. Fuel 100 octane No. aviation fuel L refined, undoped, commercial aviation lubricating oil, 115-125 S. U. at 210 F. was employed] Additives Result None A 1 B 1 30 est length, hours--- 20 50 50 acquer rating 49 17 7 istqn ring weight loss, gm. 5.95 0.29 0.11 eating weight loss, rug/cm. 0.14 0.18 0.18 sed oil properties:

Saponiiicetion No., 'f 1.7 3.5 2 5 Neutralization No., M 10.2 0.8 0.8 Iso entane insolubles, per cent w. .47 L2 C orolorm insolubles, per cent w. .18 -1 Viscosity (cs.) at- 1 Additive A=calcium salt of methylene bis p-isooctylphenol,

1% sulfate ash, sulfurized wax olefin, added sulfur or delta S=0.l%.

|additive B =additive A+0.05% sulfate ash of calcium petroleum one o.

Norm-Test is normally 50 hours in length. Undoped oils fail at lorter times due to severe wear of piston rings resulting in excessive low-by and oil consumption.

bases as primary, secondary, tertiary and quaternary amines.

Examples of detergent; forming acids are the various fatty acids of, say, 10 to 30 carbon atoms,

wool fat acids, parafiin wax acids (produced by oxidation of parafl'in wax), chlorinated fatty acids, rosin acids, aromatic carboxylic acids including aromatic'fatty acids, aromatic hydroxy fatty acids, parafiin wax benzoic acids, various alkyl salicylic acids, phthalic acid mono-esters, aromatic keto acids, aromatic" ether acids; diphenols as di-(alkylphenel) sulfides and disulfides, methylenebis alkylphenols; sulfonic acids such as may be produced by .treatment of alkyl aryl hydrocarbons or high boiling petroleum oils with sulfuric acid; sulfuric acid mono-esters; phosphoric, arsenic and antimony acid monoand (ii-esters, including the corresponding thio phosphoric, arsenic and antimony acids; phosphonic and arsonic acids, etc.

Additional detergents are the alkaline earth phosphate di-esters, including the thiophosphate di-esters; the alkaline earth diphenolates, specifically the calcium and barium salts of diphenol 0 mono and poly sulfides.

Non-metallic detergents include compounds such as the phosphatides (e. g. lecithin), certain fatty oils as rapeseed oils, voltolized fatty or mineral oils, etc.

An excellent metallic detergent for the present purpose is the calcium salt of oil soluble petroleum sulfonic acids. This may be present advantageously in the amount of about 0.025% to 0.2% sulfate ash.

Antioxidants comprise several types, for example alkyl phenols such as 2,4,6-trimethylphenol, pentamethylphenol, 2,4-dimethyl-6-tertiarybutylphenol, 2,4-dimethyl-6-octylphenol, 2,6-di-tertiary-butyl-4-methylphenol, 2,4,6 tritertiary-butylphenol, etc.; amino phenols as benzyl amino phenols; amines such as dibutyl' containing a minimum of carbon atoms.

We claim as our invention:

1. A low ash content lubricating oil for high temperature internal combustion engines containing an oil-miscible metal salt of the condensation product of an aldehyde and an arcmatic hydroxy compound in amount sufiicient to give high temperature detergent action, but not exceeding about 0.2%, based on sulfate ash, and an oxidation-inhibiting quantity of an oilsoluble, sulfur-containing, organic compound possessing antioxidant, properties, which sulfur compound is free from metallic radicals, has not more than a single polar radical and possesses a minimum of '7 carbonatoms.

2. An aviation lubricating oil containing from about 0.04% to 0.2 based on sulfate ash, of an oil-miscible metal salt of the condensation product of a low molecular weight aldehyde and an aromatic hydroxy compound and from-about 0.05% to 0.2%, based on added sulfur, of an oil-soluble, organic, sulfur-containing antioxidant, substantially free from polar and 'metallic radicals and the the

6. The composition of claim 2 wherein the aro-- matic hydroxy compound is an oil-soluble alkyl phenol.

the

7. The composition of claim'2 wherein the aromatic hydroxy compound is an alkyl naphthol.

8. The composition of claim 2 wherein the aromatic hydroxy compound is an octyl phenol.

9. The composition of claim 2 wherein the antioxidant is a sulfurized wax olefin having a molecular weight of about 225 to 425.

10. The composition of claim 2 wherein the antioxidant is a, compound of the formula RSSR' wherein R and R are hydrocarbon radicals.

11. The composition ,of claim 2 which additionally contains a detergent quantity of calcium salt of oil-soluble petroleum sulfonic acid.

12. The composition of claim 1 wherein the oil is an aviation lubricating oil having a Sayboll Universal viscosity of about -125 seconds at 210 F.

13. The composition of claim 1 which additionally contains an oil-soluble detergent.

14. The composition of claim 2 wherein the sulfur-containing antioxidant is a wax disulfide 15. An aviation mineral lubricating oil containing from about 0.04% to, 0.2%, based on sulfate ash, of an oil-solublecalcium salt of the condensation product of formaldehyde and an oil soluble alkyl phenol, and from about 0.025% tc 0.30%, based on added sulfur, of an oil-soluble sulfur-containing, parafiln wax, oxidatior inhibitor.

' JOHN R. GRIFFIN, JR.

PAUL R. VAN ESS.