US2902983A - Method of operating internal combustion engines - Google Patents

Description

United States Patent METHOD or OPERATING INTERNAL COMBUSTION ENGINES Jesse'B. Patherg, Union, N.'J.,' assign'or to Esso Research -"arid Engineering Company, a corporation of Delaware No Drawing. Applicatin'December 31, 1953 Serial No. 401,692

The present-invention concerns a method of reducing the octane number requirement increase that internal combustion engines, andparticularly' automotive engines, experience when they are operated on conventional gasolines and lubricants. More particularly, it relates to a, method of preconditioning automotive enginesby operating them on selected gasolinm and lubricants whereby the engines may thereafter be operated on conventional gasolines and lubricants without incurring undue increases in their octane number requirements. It especially relates to a method for preco'ating the walls of the combustion chambers of an automotive engine with a material whose presence reduces the amount of carbonaceous deposits 'that would otherwise beformed thereon by the use of conventional fuels and lubricants.

The existence of carbonaceous deposits in the combustion chambers of automotive engines has been a continuing problem that has confronted both the automotive industry and the petroleum'industry. As a result of extensive research work, it has now been fairly well established that the amount and attending harm of these carbonaceous deposits are influenced by several factors. First, it has been found that a number of constituents contained in conventional gasolines contribute materially toward the formation of these deposits. Such constituentsin'clude'high'boiling aromatic hydrocarbons, 40 diolefinic hydrocarbons, nitrogen compounds, sulfur compounds (especially in leaded fuels), etc.

It has also been established that a number of materials in conventional automotive lubricants'are also responsible for the formation of the carbonaceous deposits. Such materials includethose hydrocarbons that boil above about 600 F. (at 10 mm.Hg absolute) and that are generally present in lubricating oils. They also include bright stock fractions, various conventional, lubricant additives, aromatic-type hydrocarbons, etc.

It has also'been observed that carbonaceous deposits are particularly apt to develop within the combustion chambers of an automotive engine when the engine is operated under mild loading conditions for extended periods of time. Conditions such as these occur in the stop-and-go type of driving that generally prevails in urban districts. High speed or substantially full load operation, on the other hand, tends to reduce these carbonaceous deposits.

The carbonaceous deposits that form in the combustion chambersof an automotive engine have several adverse eflects. They reduce the volume of each com- 'bustion chamber and thereby increase the compression ratio of the engine. This increase-in compression ratio in turn causes a' proportional increase in the octane number requirement of-the engine. 'This increase, however, accounts for'only aboutl'0%20% of the octane number requirement increase that can be traced substantially directly to the presence of'the deposits. The remaining"80%90% of the'octane number requirement increase (ORI) appears to result from other factors that are occasioned by the existence-of the deposits. It is leaded gasoline.

contemplatedfor example that the depositshave' a catalytic effect on the combustion process that occurs'in each combustion chamber which tends to cause detonation and/or preignition. It is also contemplated that these deposits tend to insulate each combustion chamber by decreasing the rate of'heattransfer'through the cylinder walls. This results in heating up the incoming fuel-andair charge and raises the overall combustion temperature which in turn makes the engine more prone to knock.

The exact nature or structure of these carbonaceous deposits is still the subjectof'much' study and speculation. It has been reasonably well ascertained that the organic portion ofthedeposits generally contains carbon, hydrogen and oxygen in an atomic'ratio of about 5 :5 :2. The deposits may 'also contain inorganic constituents as, for example, various lead-compounds when the engine under consideration has'been operated on a In theseinstances'the inorganic portion of the'deposits may comprise up'to about 'to by weight of-the deposits. Even here, however, it is now considered that the presence or existence of'the inorganic deposits may be largely dueto the existence or presence of the carbonaceous deposits. In other words, the inorganic deposits are held Within the combustion chambers by the resin-like structure of the carbonaceous deposits; and the inorganic deposits can be avoided if the carbonaceous deposits can first be prevented from forming.

Although the automotive industry and the petroleum industry are aware of the existence of the deposits described above, relativelylittle progress has as yet been made toward a practicaland complete solution to the problem-of eliminating them. Such a solution isurgent,

since the present alternatives present somewhat of a dilemma. The automotive engine'manufactu'rers are reluctant to build engines that have compression ratios much in excess of 8/1 since'engines of greater compression ratios than this require very high octane gasolines afterrelatively short operating periods. Thus, an engine will generally experiencean'increaseinits octane requirement (O.R.I.) of 10 to 20 octane numbers in 10 to 20,000 miles of its operating life. This requirement increase .presents a very serious problem and, in effect, deprives thegeneral public of theopportunity to take advantage of the increased operating-economies of high-compression engines.

The petroleum industry on the other hand is faced with the necessity of providing extremely high octane fuels (95-100 O.N.) to satisfy engines of greater than 8/1 compression ratio, unless-a means is found whereby these engines may operate without knocking on conventional, commercial gradefuels of less than 95 ON. and preferably less than ON. Otherwise, the petroleum refiners will be forced to provide fuels that are extremely expensive and that entail complex refining operations.

Accordingly, it is an object of the present'invention to make available a means for preconditioning an automotive engine wherebythe engine may be operated on conventional gasoline-type fuels and lubricants without experiencing an undue increase in its octane number requirement.

It is a particular object of the present invention to provide a gasoline fuel which is to be utilizedin the operation of the engine during its break-in-period and which will thereafter permit satisfactory performance of the engine on conventional fuels and lubricants.

These objects may be achieved in accordance with the present invention in a manner which will be described in detail hereinafter. Briefly, however, the present invention comprises operating a new automotive engine or an engine which is substantially free of carbonaceous deposits on a gasoline and a lubricant which will hereinafter be identified as non contributing materials. The term non-contributing) as used herein is intended to designate those fuels and lubricants which form substantially no carbonaceous deposits when they are employed in an automotive engine. Quantitatively speaking,'a non-contributing gasoline is considered to be a gasoline that possesses a resinification index of less than 40 and preferably less than 20 mgs./200 g. A non-contributing lubricant is considered to be a lubricant that has a resinification index of less than 10 and preferably less than mgs./ 5 g. The exact definition of the term resinification index will be presented a little later in this description. The benefits of the present invention are best realized when a new or clean engine is initially operated on a combination of a fuel that has a resinification index less than about 15 mg./200 g. and a lubricant that has a resinification index of about 3 mg./5 g. or less. It will be noted that conventional, commercialgrade gasolines and lubricants have resinifieation indexes of about 40 to 100 or more mg./200 g. and 25 to 60 or more mg./5 g. respectively. Fuels and lubricants in these latter ranges may be referred to as contributing fuels and lubricants, since they will contribute toward the octane requirement increase of an engine in which they are employed.

The present invention further contemplates that the non-contributing fuel contain a hydrocarbon-soluble compounds of at least one of the following metals: chromium, copper, manganese, zinc, nickel, cobalt, cadmium, molybdenum and iron. The metal compound, in addition to being hydrocarbon-soluble, must be capable of forming an oxide of the metal under the combustion conditions that exist within the combustion chambers of a conventional automotive engine.

In further accordance with the present invention, an automotive engine is operated on a metal-containing,

non-contributing fuel in combination with a non-contributing lubricant (of the types briefly defined above) for a period of time suflicient to provide a layer of the oxide of the metal on the interior wall surface of each combustion chamber within the engine. The required length of time will be brought out in detail later in this description. It is critical, however, that this operating procedure be employed before the engine is operated on a fuel and/ or lubricant which would cause any buildup. of carbonaceous deposits with the engine. In other words, it is critical that any given automotive engine be operated in accordance with the present invention before it is operated on a conventional fuel and/or lubricant. As demonstrated later herein, the teachings of the present invention cannot be completely realized without adhering to this operating sequence.

As mentioned above, the present invention requires the use of gasolines and lubricants that have resinification indexes of less than 40 mg./200 g. and mg./5 g., respectively, preferably less than 20 mg./200 g. and 5 mg./5 g., respectively, and especially less than mg./ 200 and 3 or less mg./5 g., respectively. The term resinification index refers to the relative freedom of a fuel, lubricant or other material from a tendency to form tenaciously adhering, resin-like, carbonaceous deposits when it is subjected to combustion in a container under a hot, smokeless flame, e.g., a hydrogen flame. In accordance with the Combustion Test for Resinification Index (as described in detail in copending application Serial No. 352,373 filed in the name of Alexander H. Popkin on May 1, 1953, now Patent No. 2,761,- 766) a known weight of a sample of material to be tested such as a lubricating oil, a gasoline or other material is placed in an open vessel having smooth nonabsorptive inner surfaces such as a glass beaker, porcelain crucible, etc. A hot, smokeless, clean flame and preferably a hydrogen flame (although other clean flames such as methane, etc. may be used) is directed into the opening of the vessel. The burner tip, for introducing the gas and air or oxygen (if needed), is directed toward the interior of the vessel. The sample is burned until only a dry residue remains. The flame is discontinued and the vessel is allowed to cool. The total weight of the resinous residue is then determined. When testing oils, the interior of the vessel is wiped carefully, before weighing, with a soft cloth or other soft material to remove carbonaceous deposits but to leave the tenaciously adhering resin-like deposits. The total deposits are weighed when burning fuels. The weight of deposits in mgs. for a given weight or charge in gms. gives the resinification index. Specific testing conditions used for oils, additive-containing oils, additives, and gaso lines are shown below:

The combustion test described above has been found to accurately predict the amount of combustion chamber deposits that a gasoline, lubricant or similar material will form within an automotive engine which is operated under actual road conditions. It has also been found to correlate with another prediction test procedure which is carried out in a single cylinder Lauson engine. The Lauson engine test in turn has been found to correlate with results obtained under actual driving conditions in conventional automobiles.

Single cylinder Lauson engines are well known in the art and are widely used therein for various studies of petroleum lubricants, fuels and so forth. The particular Lauson engines employed in the tests that are referred to in the present description had a 6.5/1 compression ratio head and were operated with an induction motor at 1840 r.p.m. and 0.5 BKW (brake-kilowatt) load.

Each test was usually run for a period of about 70-200 hours with the particular lubricant or fuel being tested and with a spark advance of 12 BTDC. The ratings were conducted with secondary reference fuels using an oscilloscope which gave visual ratings of knock intensity via a sensitive pickup attached to one of the studs of the engine. This procedure was found to be more accurate than the audio-type ratings usually used in the Standard Uniontown procedure, because knocking in the Lauson engine is difiicult to hear. Operations at the low power level of 0.5 BKW have been established to provide good correlations with full scale road tests. In other words, the Lauson engines experience octane requirement increases (O.R.I.) that are directly related (though not necessarily equal) to the requirement increases that are experienced by full scale automotive engines in actual road performance.

As described above, gasolines that are satisfactory for the purpose of the present invention include those gasolines which have a resinification index of less than 40 mg./20O g. Such gasolines may be produced from fractions including isooctane; alkylate; virgin naphthas boiling below about 300 F. and preferably below 250 F.; high octane polymers prepared by the catalytic polymerization of lower molecular weight olefins, hydroformates prepared by hydroforming naphthenic-type hydrocarbon distillates to form high octane aromatic components, reformed gasoline fractions prepared from straight run gasolines using conventional platinum catalysts, metal oxide catalysts and the like; catalytic cracked naphthas prepared by cracking gas oils, residuals, etc., in the presence of metal oxide catalysts such as silica-alumina, silica magnesia, and the like; and various other types of comescapee 'ponents that are conventionally employedin gasolines.

Such gasolines are usually formulated by mixing two or more of the above general types ofcomponents in order to form gasolines meeting octane requirement, vapor pressure, stability, and other specifications.

It has generally been found of the various hydrocarbon 'cornpounds present in gasolines that parafiins, 'naphthenes and mono-olefins will not contribute substantially to ORI. Aromatic components, particularly those having a' boiling point higher than tolue'ne contribute substantially to octane requirement increase. Those boiling above about 300 F. are especially undesirable for this purpose. Therefore it is preferred that the gasoline contain no more than 20% by weight of aromatic hydrocarbons boiling above about 300 F., and more especially less than about 20% by weight of aromatics boiling above about 250 Lead tetraethyl is used in most commercial gasolines in concentrations ranging from about" 0.1 to 3.0 cc./ gallon Lead scavenging advantage in decreased ORI canbe achieved by lowering the sulfur content of gasoline critically below the level at which the sulfur has any effect on the actual octane number of the gasoline containing tetraethyl lead. For minimizing ORl'it is important to decrease the sulfur content of leaded gasoline below about 0.02% and pref erably below about 0.005% by weight. This may be achieved by treating the various components that go into the gasoline, in order to reduce the sulfur content to relatively non-contributing amounts.

Treating procedures for sulfur reduction include prompt caustic washingofthe sulfur-containing material in the absence of oxygen soon after a catalytic cracking operation; hydrofining of cracked naphthas in which the naphtha is treated with a catalyst in the presence of hydrogen; treating naphtha with formaldehyde at elevated temperatures with or without sulfuric acid; and treatment of sulfur-containing naphthas with finely divided sodium in the presence of secondary or te'rtiary' alcohols, ethers or ketones. The'extent to which'any or all of'the components are treated 'will' of necessity 'depend' on the amount fuel is leaded with tetraethyl lead and non-contributing amounts ofaromatics.

In order to minimize the contribution of a conventional leaded gasoline containing a normal complement of sulfur, say above 0.1% by weight, a lead scavenging agent that is relatively high boiling may be added to the fuel. Although it is conventional to use such materials as ethylene 'dibromide and the like as scavenging agents, these materials are not so effective for complete removal of lead as the higher boiling scavenging agents including halogenated aliphatic hydrocarbons such as hexacblorobutadiene; halogenated alkyl aromatics such as bromo xylenes, including mixed dibrornoxylenes, dibromo toluenes; 3,4dichlorocumene; l,2-'dibromobenzene; 1,2,4'trichlorobenzene; 2,4dichlorotoluene; their mixtures and the like. Higher boiling means those agents having 'substa'ntially the volatility characteristics of tetraethyl leadipreferablythey 'have'vaporpressures at 120 F. of about 05m 5.0 mm. Hg. In' excess of about 0.5 and 'preferably above about 1.0'stoichiometrical equivalents of these agents, based on the TEL, may be added to the cate ""anddi-C 0x0 alcohol sebacate.

fuel. Such higher boiling scavenging agents are taught in such U .S. Patents as-2,496,983; 2,574,321 and 2,479,-

-The .gasoline fuel may also contain other addition agents such as antioxidants, guminhibitors, solvent oils, rust inhibitors, metal dea'ct'ivators, etc.

A gasoline fuel that is'particularly preferred for the purposes ofthe' pres'ent'invention is substantially pure iso-octane. Typical inspections for such a fuel are presented in the following table.

'TABLE'I -Fuel' inspections Gravity, API 71.3 R.V.P.,p.s.i 1.8 Research octane'No 99.1 Motor octane No.- 98.8 Sulfur, weight percent 0.0008

Olefins, wt. percent 0 Aromatics, Wt. percent 0 Engler Distillation:

IBP 205 50% ofi, F. 210

FBP., F 264 1 Atmospheric pressure.

about 3 mgI/S g. Suitable lubricants have been presented,

described and claimed in Serial No. 375,158 filed in the name orr'ednar'd E. Moody and Alexande'r'I-I. Popkin on August 19, I953. Suitable additive containing lubricants are described andclaimedin patent application Serial'No. 375,138'filed in thena'me of LeonardE. Moody and Alex- "arider H. Popkin o'n August l9, 'l953, now abandoned. Thus, suitablelubricantsinclude distillate mineral lubricating oil frac'tionsboilingbelowab'o'ut'S 75 F. at 10 Hg absolute) derived from crude oils which in turn are derived from an or Hie-conventional crude oils. Those distillates derived from 'theMid-Continent fields, however, are preferred because of their excellent viscosity characteristics.

The preferred mineralbil'base stocks of the present tion at a pressure of 10 mm. Hg) have been removed. A suitable boiling ran'ge'is within about 275 to 575 F.,

"or'pr'efera'blywithin about 300 to575 F., at 10 mm. Hg pressure'absolute, with less than about 5 to 10% of 'co'mponentsboiling above 550 F. and less than about 5 to 10% 'co'mponents boiling below 390 F. The lower end of 'the'boiling range affectsto a large extent oil consumption characteristics or the lubricant, and generally componentsboil'ingmuc'h below about 275F. to 325 F. at'10-'"mm. 'Hgabsolute are too high in volatility for use in many high compression ratio internal combustion engines. The distillation testis lASTM Method D 1160- 52 T.

Other suitable 'base' stock constituents and blending agents include low' resinification index hydrogenated oils, synthetic oils resembling petroleum oils (polymerized ole- 'fins,'synthesis productsfrom the'reaction of oxides of carbon with'hydrogen or f'rom hydrogenated coals, shale oil derivative, etc.), formals, synthetic polyester and polyether-type'lub'ricants and the like. Synthetic oils include esters made from a monohydric alcohol and a monohydric organic acid or diesters made from alcohols and dibasic acids. Specific examples include di-2-ethylhexyl seba- Alcohols include the C C C C C and C alcohols made by the 0x0 process'from' olefins. 'Suitable dibasic acids in- '7 clude adipic, azaleic'and sebacic acid. Complex esters made from a monohydric alcohol, a dihydric alcohol (glycol) and a di'basic acid may also be used. Polyalkylene oxide-type synthetic oils, simple formals, complex for- Gravity API 12.8 Viscosity SUS 100 F 178.0

210 F 48.6 Conradson carbon 0.098 Resinification index Pour pt. F -35' Ash 0.0057% (Wt).

The non-contributing fuels of the present invention must contain a hydrocarbon-soluble compound of at least one of the following metals: chromium, copper, manganese, zinc, nickel, cobalt, cadmium, molybdenum and iron. It is critically necessary that the hydrocarbon-soluble compound react under the conditions prevailing within the combustion chambers of a conventional automotive engine to form an oxide of the metal or metals selected.

Suitable compounds of the above metals include the gasoline-soluble salts or chelated compounds formed by their reaction with alcohols, phenols or organic acids. Preferred compounds are the metal derivatives of betadiketones; and particularly preferred compounds are the pentanediones of these metals.

An especially preferred fuel additive for the non-contributing fuels of the present invention is a mixture of about 80% by wt. of cobalt pentanedione and about by wt. of chromium pentanedione. The mixture is preferably added to a fuel in the form of a concentrated solution in a solvent such as a non-contributing gasoline.

Other suitable additives include carbonyl compounds such as nickel carbonyl, cobalt carbonyl, and iron carbonyl. Hvdrocarbonyls such as iron hydrocarbonyl and cobalt hydrocarbonyl may also be employed.

Summarizing momentarily, it is preferred that an automotive engine of the type described herein be operated on a lubricant consisting of a non-contributing motor oil of the polypyropylene oxide type and a fuel consisting of isooctane containing a mixture of chromium and cobalt pentanediones. The automotive engine must be operated for a period of time suflicient to provide a layer of metallic oxide on the surfaces of each combustion chamber that will be sufficient to prevent the formation of carbonaceous deposits thereon. This time period will vary depending on the characteristics of the engine involved and the concentration of the additive in the break-in fuel. This time and additive concentration should be adjusted so that there will be consumed an amount of fuel equivalent to 0.01 to 1.0 grns. of the metallic element or elements per square inch of clearance volume surface. An amount of fuel equivalent to about 0.1 gms. of the metallic element or elements per square inch of clearance volume surface is especially preferred.

The preferred concentration is such that the break-in procedure will require a maximum of ten and preferably less than five hours, although many permutations may be used to suit the convenience of the operator. This is amplified further in the following examples.

The following examples are presented to more clearly illustrate the nature and advantages of the present invention. The examples were obtained by using diiferent fuels and lubricants in various combinations. Each of the fuels and lubricants is described briefly below FUELS Fuel 1 consisted of substantially pure, synthetically prepared iso-octane.

Fuel 2 was a conventional commercial leaded gasoline consisting of a blend of iso-pentane, catalytically cracked naphthas, and virgin naphtha.

Fuel 3 Was another" conventional commercial motor gasoline comprising a blend essentially the same as Fuel 2.

LUBRICANTS Lubricant A was a synthetic lubricant of the polypropylene oxide type.

Lubricant B was a commercial-grade motor oil which consisted of a blend of an extracted Mid-Continent distillate and a deasphalted, dewaxed residuum.

Typical inspections of the fuels identified above are presented in the following table:

TABLE II Fuel inspections Fuel 1 Fuel 2 Fuel 3 Gravity, API 71. 3 64. 0 59.0 R.V.P., psi l. 8 8. 5 8.5 Research Octane N0 99.1 94. 0 88.0 Motor Octane No. 98. 9 83.0 80.0 Sul ur, Wt. Percent 0. 0008 0. 07 0.08 Olefins, Vol. Percent. 0 35. 40 30. 35 Aromatics, V01. Percent O 15. 20 l0. l5 Resinification Index, Dig/200 g 13 Engler Distillation: IBP, F 205 110 50% Off F 210 210 230 BR, F 264 380 410 l Atmospheric pressure.

Typical inspectionsof the lubricants described above are presented in the following table.

TABLE III Lubricant inspections Example 1.A Lauson engine of the type described earlier in this description was operated for a period of 73 hours on Fuel 1 and Lubricant A. In this case, Fuel 1 contained 2.0 cc. per gallon of a solution comprising a mixture of chromium and cobalt pentanediones in a hydrocarbon solvent. This additive solution contained 0.07 gram of the mixed pentanediones per cc. of solution distributed as follows: 79.6 weight percent of the cobalt compound and 19.9% by weight of the chromium compound, and 0.5 weight percent unknown impurities.

At the start of the test the octane requirement of the clean engine was determined by the use of secondary reference fuels in a conventional manner and was found to have an octane requirement of 47. After the 73-hour operating period, the octane requirement of the engine was again determined and found to be still 47. These results clearly establish the fact that the lubricant and the fuel were both non-contributors and that the addit-ive employed had no adverse effect on the octane requirement of the engine.

Example 2.The engine employed in Example 1 was again operated on Fuel 1 and Lubricant A but in this this instance the fuel contained 100 cc. per gallon of the additive described in Example 1. In this instance, the engine was operated for a period of 2.5 hours for the IExdmple-?3.After thesteps'de'scribed in Examples 1 r"- and 2 were completed, the Lauson engine described in those examples was then operated for a period of about 80 hours on Fuel 1 containing no additive and Lubricant B. Following the 80-hour period of operation, the octane requirement of the engine was determined and found to have remained at a value of 47. Thus, the preformation within the combustion chamber of the layer of cobalt and chromium oxides operated successfully to completely eliminate any increase in the octane requirement of the engine when it was switched to a lubricant which had been found to be a definite offender in this regard. The extent to which this conventional lubricant is an offender is brought out more clearly in Example 6 which is presented later herein.

Example 4.A Lauszon engine with an initial octane requirement of 54 was operated for a period of 182 hours on a combination of Fuel 2 and Lubricant A. The fuel in this instance contained 4 cc. of a gallon of the additive described in Examples 1 and 2. Unlike the results obtained in those examples, however, the engine in the present example experienced an increase in its octane requirement about octane numbers after 44 hours of operation, and 14 octane numbers after 182 hours of operation. It is apparent from. these results that the use of the fuel additives that are specifically advocated in the present description is not effective in preventing an increase in the octane requirement of an engine unless the additives are introduced within the engine before the engine is operated on fuel and/or lubricant compositions that are known to be offenders in this respect. In this instance the lubricant was a non-contributor but the fuel was a definite contributor.

Example 5 .A Lauson engine having an initial octane requirement of 56 was operated for a period of 190 hours on Fuel 1 and Lubricant B. After 70 hours. of operation, the octane requirement of the engine increased to a value of 64. After 190 hours, the octane requirement of the engine increased to: a value of 73. It is clear from the data obtained in this example and in example 3, above, that the fuel additives of the present invention are extremely effective in reducing the octane requirement of an engine when the procedure for introducing the additives within the engine which is spelled out in the present description is adhered to. Thus, it will be observed that the engine of Example 3, which was operated on the same fuel and lubricant composition as the engine in the present example, experienced no increase in its octane number requirement. The engine in the present example, on the other hand, experienced an octane requirement increase of about 8 units after being operated for substantially the same period of time as the engine in Example 3.

The present example also clearly demonstrates that the octane requirement of an engine will increase very substantially if the engine is operated on a lubricant that has a high resinification index. This result will occur even though the fuel in the engine is of the non-contributing type.

Example i6.-In this example a conventional Plymouth engine was operated on Fuel 3 and Lubricant B for 3500 miles. The octane number requirement increase experienced by the engine in this instance was 8.4 octane numbers.

The engine was then overhauled, and the deposits existing in the combustion chambers of the engine were completely removed. The engine was then operated for another 3500 miles on Fuel 3 and Lubricant B, but in this instance the fuel contained 4 cc. per gallon of the additive 10 described inExam'ple 1 above. D'firing'this'test the octane requirement of the engine increased 9.5 octane numbers, thereby again demonstrating that it is a critical feature of thepresent invention to (1) operatethe' engine initially on non-contributing fuels and lubricants in' com bi-natio'n and (2)'to incorporate within the non-contribuh ing fuel the presently defined additives.

It will be particularly noted that the data obtained in the present example agree very well with the data obtained in Example 4 in that both examples show that it is substantially useless to employ the fuel additives of the present invention without also employing non-contributing fuels or lubricants during the initial operation of the engine.

What is claimed is:

l. A method of operating an internal combustion engine having a compression ratio of at least about 7/1, which comprises initially operating the engine on a noncontributing lubricant having a resinification index less than 10 ing/5 g. and a non-contributing gasoline having a resinification index less than 40 mg./200 g.; said noncontributing gasoline containing a gasoline-soluble metal compound selected from the class consisting of the gasoline-soluble compounds of chromium, copper, manganese, Zinc, nickel, cobalt, cadmium, molybdenum and iron; said compound being of a character to provide an oxide of the metal under the conditions within the combustion chambers of the engine; and thereafter operating the engine on a gasoline and lubricant combination ordinarily forming excessive deposits within the combustion chambers of the engine.

2. A method as defined in claim 1 in which the engine is operated on the non-contributing gasoline and lubricant for a period of time adapted to consume from 0.01 to 1.0 gms. of the metal in the metal compound per square inch of clearance volume surface in the engine.

3. A method as defined in claim 2 in which the gasoline is iso-octane and the non-contributing lubricant is a synthetic oil of the polypropylene oxide type.

4. A method of operating an internal combustion engine that has a compression ratio greater than 7/1 which comprises initially operating the engine on a non-contributing gasoline having a resinification index less than 40 mg./20O g. in combination with a non-contributing lubricating oil having a resinification index less than 10 mg./5 g.; said gasoline containing a gasoline-soluble metal compound selected from the class consisting of the gasoline-soluble compounds of chromium, copper, manganese, zinc, nickel, cobalt, cadmium, molybdenum and iron; said metal compound being adapted to form an oxide of the metal under the conditions that prevail within the combustion chambers of the engine; consuming an amount of said gasoline equivalent to from about 0.01 to 1.0 gms. of the metal per square inch of clearance volume surface in the engine; and thereafter operating the engine on a conventional gasoline having a resinification index greater than 40 mg./200 g. and a conventional lubricant having a resinification index greater than 10 mg./5 g.

5. A method as defined in claim 4 in which the noncontributing gasoline has a resinification index less than 20 mg./200 g. and the non-contributing lubricant has a resinification index less than 5 mg./5 g.

6. A method as defined in claim 5 in which the noncontributing gasoline has a resinification index less than 15 mg./ 200 g. and the non-contributing lubricant has a resinification index of about 3.

7. A method as defined in claim 6 in which the gasoline-soluble compound is a pentanedione.

8. A method as defined in claim 7 in which the compound is a mixture of cobalt pentanedione and chromium pentanedione.

(References on following page) References Citedin the file bf this patent 7 UNITED STATES, PATENTS Barnard Dec. 15, 1942 12 Malott Dec. 12, 1944 Taylor July 26, 1949 Bartleson July 17, 1951 Hays Nov. 9, 1954 Trimble et a1. Sept. 4, 1956

Claims (1)

1. A METHOD OF OPERATING AN INTERNAL COMBUSTION ENGINE HAVING A COMPRESSION RATIO OF AT LEAST ABOUT 7/1, WHICH COMPRISES INITIALLY OPERATING THE ENGINE ON A NONCONTRIBUTING LUBRICANT HAVING A RESINIFICATION INDEX LESS THAN 10 MG./5 G. AND A NON-CONTRIBUTING GASOLINE HAVING A RESINIFICASTION INDEX LESS THAN 40 MG./200 G., SAID NONCONTRIBUTING GASOLINE CONTAINING A GASOLINE-SOLUBLE METAL COMPOUND SELECTED FROM THE CLASS CONSISTING OF THE GASOLINE-SOLUBLE COMPOUNDS OF CHROMIUM, COPPER, MANGANESE, ZINC, NICKEL, COBALT, CADMIUM, MOLYBDENUM AND IRON; SAID COMPOUND BEING OF A CHARACTER TO PROVIDE AN OXIDE OF THE METAL UNDER THE CONDITIONS WITHIN THE COMBUSTION CHAMBERS OF THE ENGINE; AND THEREAFTER OPERATING THE ENGINE ON A GASOLINE AND LUBRICANT COMBINATION ORDINARILY FORMING EXCESSIVE DEPOSITS WITHIN THE COMBUSTION CHAMBERS OF THE ENGINE.