CA1072074A

CA1072074A - Synthetic crankcase lubricant

Info

Publication number: CA1072074A
Application number: CA231,662A
Authority: CA
Inventors: George Berens
Original assignee: Stauffer Chemical Co
Current assignee: Stauffer Chemical Co
Priority date: 1974-12-16
Filing date: 1975-07-16
Publication date: 1980-02-19
Also published as: NZ178239A; IL47751A0; SE413324B; IE41629B1; BE832496A; AU498533B2; IL47751A; PH12459A; GB1525392A; DE2535213A1; AU8311775A; NO142405B; BR7505099A; SU902672A3; NL7509594A; DK344975A; CH615216A5; FR2295121B1; DD119815A5; NO142405C

Abstract

SYNTHETIC CRANKCASE LUBRICANT
Abstract of the Disclosure A synthetic crankcase lubricant composition compris-ing an effective amount of a base stock containing a blend of polyol ester and synthetic hydrocarbon, wherein the polyol has at least 2 methylol groups on a quaternary carbon atom.

Description

Background of the Invention This inven ion relates to synthetic lubricants and more particularly to synthetic crankcase lubricants having a base stock comprising a liquid polyol ester and a liquid synthetic hydrocarbon. It has been discovered that lubricants of this type are particularly adapted to automotive crankcase use.
The use of various diesters, polyesters and complex esters as lubricating oiis is well known in the art and has been described in various patents, eOg. U.S. Patent 2,723,286;

2,743,234 and 2,575,196. Naturally occurring fats and oils, predominantly glyceride esters, have been used as lubricants for many centuries. More recently, synthetic esters or syn-thetic ester blends prepared from various combinations of mono-and polyfunctional acids and alcohols have been developed for lubricant use.
Synthetic esters have been widely used as turbine engine lubricants, however, there has been little use made of them in piston engines. The reason for their lack of acceptance as piston lubricants has been primarily due to the deleterious effect of excessive swelling that these esters have had upon the elastomer seals used in piston engines.

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Seal "swell" is defined as the amount in percent that the volume of elastomer seals expand upon contact with, and exposure to the lubricant environmënt under engine operating conditions. Insufficient or excessive swell causes the seals to lose their ability to retain and confine the engine fluids.
Leakage occurs which can cause a high amount of oil consump~
tion.
:~ ~ 3 A controlled seal swell is, therefore, one of the most important characteristics of a crankcase lubricant. It is essential that the lubricant employed be capable of impart~
ing a controlled swelling of the enginé's elastomer seals, i sufficient to prevent lea~age of lubricant.
The polyol ester-synethetic hydrocarbon base stock of the present invention shows excellent properties with elastomer seals, particularly those sold under the trademark Buna-N (a copolymer of butadiene-acrylonitrile).
While the capability of not causing excessive or in-sufficient elastomer swell,is a valuable characteristic, : ~., .-, .
lubricating compositions used in piston type internal com-bustion engines, hereafter referred to as piston engines, must also possess other special characteristics in order to ~-satisfactorily fulfill the speci/al requirements placed upon lubricants for this type of engine.
It is essential that these lubricants possess suf-ficient lubricity to enable their use under severe operating conditions. They must also be oxidatively and thermally stable, and resistant to the formation of rust, sludge and varnish.
The viscosity characteristics must be such that the lubricant can be used over a wide temperature range; that is, adequate - . .

viscosity at high temperature, low viscosity at low tempera~
tures and a low rate of change of viscosity with temperatur~
Its pour point should be low. Its volatility should be low at elevated temperatures o-E use; that is, selective evaporation .
or volatilization"of any important component should not take place at high temperatures of use. .',~
The wide-spread advance of piston engine powered vehicles has led to the use of piston engine equipment in global areas where ambient temperature conditions are much more :
severe than the tempera~ure conditions generally encountered in temperate climates of the United States and other densely .' "
populated areas of the world. Engine oils must now be suf- :~
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iciently liquid at temperatures as low as -65F. to allow the ,~: , engine to start, yet have volatility properties sufficient ~'~
; to preclude evaporation when exposed to temperatures near 350F.
~:, over prolonged periods of time. .
Coupling all these properties with compatibility to- .
wards a variety o~ elastomers is a difficult achievement for a .
functional fluid. The base stock is genexally combined with ~:'20- an additive package designed to maximize the special character- .-istics required by the lubricant. In order to accomplish this, ,~' the base stock must have additive compatibility. .
Additive compatibility is defined as the additive's :;
ability to become homogeneously dissolved or dispersed in the '' base stock, and is a measure of the additivels ability to avoid , ,,-hazing, flocculating or settling out of the base stock fluid.

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Petroleum lubricants, which have heretofore been usea in piston engines almost exclusively, are generally incapable of providing both the high and low temperature requirementS ncedea today. Petroleum oils can be modi~ied, for example, by adaition of kerosene to proviae lo~ temperature starting, but when this low temperature modification is effected, ~he lubricants become too volatile for continuea high spee~, high temperature operation.
Conversely, petrole~m oils can be mo~ified to provide good high ~;
, ; temperature performance, but such compositions generall~ become ) so viscous at low temperatures that they do not ~unction proper~y . .
in cold weather.
:: , Conventional synthetic esters commonly used for lubri-cation o~ turbine engines, while being capable of imparting some improved properties over petroleum based piston engine oils, 5 have generally been found unsuitable for use as piston lubricants.
This is dué to excessive volatility and inadequate vis-cosity properties at high temperatures. Most importantly, these ~-fluids have a tendency to cause elastom~rs used as seals in au~o-~ motive engines to swell excessively, which can result in loss of 'O lubricant by leakaye past the engine seals.
It is, therefore, surprising that the lubricant o the present inven~ion, containing a base stock comprising a polyol ;~
ester ana a synthetic hydrocarbon, was able to not only meet but exceed the rigorous requirements placeA upon an automOtive crankcase lubricant. ~ -Detailea Description of the Invention This invention relates: to a blend o~ a po~yol ester ~: ' ' ' ' - ' , '.' . ' . .
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( ~7Z~74 C-444~/4501~S14 with a synthetic hydrocar~on as the base ~lui~ in a lubricant especially suita~le for use in piston engines whi~h demons~rates excellent elastomer compatibility and impro~ed thermal stability.
The polyol esters employed in the context o~ this iDve~tio~ are the esterification reaction pro~ucts o~ an ali~
phatic monocarboxylic acid with an aliphatic polyol.
The,aliphatic monl~carboxylic acid~; u5ea in accordance with thi~ invention are compounds or mixtules o~ compounds having average chain lengths from about 4 to about 12 carbon atoms.and . . . preferably from about 5.to akout 9 carbon atoms. The indiviaual acids can range in chain length from about 2 to about 18 carbon atoms. ~ormal acids are preferred, although bran~hed monocar boxylic acids can also be used, particularly those with no more than ~wo carbon atoms in side chains.
;; 15 . In synthesi2ing the polyol esters, minor amounts of dibasic acids can be employed as crosslinking agents. The alkyl portion o the dibasic acid generally ranges from abo~t 2 to about 18 carbon atoms, more pre~erably from about 4 to about 12 carbon atoms. Particularly preferred dibasic acids include .
adipic, azelaic, isophthalic, and mixtures thereof. Also in-cludea for purposes o crosslinking are the dimer and trimer acids, and mixtures thareo~.
The polyols used are those having at least two3 ana ~ preferably three methylol groups on a quaternary carbon atom.
25 Among the polyols which can be used are trimethylolpropane, ~ trimethylolethane, neopentyl glycol, pentaerythritol, 2-butyl-. .
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C-4448/4501/~514 2-ekhyl-l,3-propanediol and 272,4-trimeth~1-19~-pentanediOl, and mixtures thereof.
Also included within the definition o~ polyols are those polyols which are f~rmed from ether condensation of ~wo or more polyols within the definition above, provided that no more than four polyol.units are SQ condensed and further pro-vided that at least our OEI groups are available.
For spark ignited engine applicakions, particularly pre~erxed polyols include penkaerythritol, trimethylolpropane;
trimethylolethane, and mixtures thereof.

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Due to its superior additive compatibility, it is especially preferred that the polyol ester be a trimethylol- ~ ^
propane triester.
In those instances where a higher viscosity ester is desirable for use in a diesel engine, then an ester of a higher molecular wèight polyol should be employed, preferably a con-densed polyol such as ditrimethylolethane, ditrimethylolpro-pane, dipentaerythritol, tripentaerythritol and mixtures thereof Due to its superior additive compatibility, it is ; ~
especially preferred that the polyol ester from use in diesel -applications be a ditrimethylolpropane tetraester.
The synethetic hydrocarbon component of the base `
stock is a liquid hydrogenated poly-alpha-olefin or alpha-olefin oligomer. The olefin constituent of the oligomer varies in carbon chain length from about 6 to about 14 carbon atoms, -~
with the preferred chain length varying from about 8 to about 12 carbon atoms, with about 10 carbon atoms most preferred, . . , ~ .
-~ because of better viscosity and temperature characteristics, 20 ~ and lower volatility. ; ~
The ester-oligomer base stock components are blended ~ ;
in amounts which are effective to impart sufficient swell to the seals. A sufficient amount of elastomer seal swell as con-templated by this invention is wherein the seal swell varies ,~.
from about 4% to about 20%, with a seal swell of about 5% to about 15% being preferred, and a seal swell of about 6% to 9%
being especially preferred for an elastomer such as Buna N, which is commonly employed in automotive crankcases.
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Viscosity is another important property. The lubri-cant must have an acceptable viscosity range to enable it to be liquid at temperatures as low as minus 65F. to allow the engine to start, and yet retain sufficient film strength to ;
adequately lubricate at operating temperatures that can ap-proach 350F.
i The acceptable viscosity of the lubricant base skock -can vary from about 3 to about 20 cèntistokes at 210F., with a preferred viscosity varying from about 4 ~o about 12 centi-,-stokes at 210F.
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The lubricant must also have volatility properties ~ -sufficient to preclude significant evaporation at temperatures of about 350F. over extended periods of time. ;~
The most effective blends of polyol ester to alpha-olefin oligomer, wherein control of elastomer seal swell is of primary concern, is where the ratio of polyol ester to :::
~ oligomer varies from about 35:65 to about 80:20 parts by weight.
::, The preferred weight ratio of polyol ester to oligomer varies from about 40:60 to about 66.7:33.3 with a ratio of about 50:50 ` 20 parts by weight being particularly preferred. The following

3, table is illustrative of controlled seal swell resulting from a typical alpha-olefin oligomer-polyol ester blend:
TABhE I
Seal swell characteristics of Buna N* with various . .i , . .
blends of trimethylolpropane triheptanoate ester and a mixture of decene oligomers~

I Blend ;~j Ester:Oligomer Ratio Seal Swell, ~
,$ ~ - , i 40:60 5~20 ,~ 30 50:50 7.93 : :.
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Blend Ester:Oligomer Blends Seal Swell, 55 45 8.98 60:40 10.64 66.7:33.3 12.53 ;
80:20 16.10 . ` ' ~ .
TABLE II
Viscosity and pour point for selected blends from Tahle I:
Ester:Oligomer_Ratio 50:50 66.7-33.3 Viscosity at 210F.
(Centistokes)..................... ..4.40 4.05 ~ ~;
100F.................. .21.15 18.79 0F.................. 421 355 -:
-40F.................. 4701 3107 Pour Point.......................... -70F. -75F.
For diesel applications, a higher viscosity polyol ester, such as that selected from the group consisting of di~
trimethylolpropane tetraesters and dipentaerythritol hexa-esters and mixtures thereof, blended with poly-alpha-olefin oligomers, provides an excellent base stock, especially from ~ ;
~ the standpoint of good viscosity and controlled seal swell ~
;~l characteristics. Table III is illustrative of these pro- ~-perties.

`j TABLE III -1 blend of di-trimethylolpropane tetraheptanoate and mixed decene oligomers.
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Properties , Viscosity at 210F. ......... 9.5 centistokes -;
Pour Point .................. -40F.
Buna N Seal Swell at 300F. after 70 hrs. ...~ 7%
The polyol ester-synthetic hydrocarbon oligomer base stock system of the present invention has demonstrated excel-lent additive compatibility without adversely effecting engine -elastomeric seals. A typical additive package for the ester-: -.
oligomer blend general]y comprises those additives which im-part anti-corrosion properties, anti-wear properties, load bearing properties, luhricity, viscosity index improving properties, detergency, dispersancy, metal deactivation, anti-foam properties and the like.
It is of particular importance that the dispersancy ~
and detergency additives be compatible and effective with the ~1-base stock blend. This is due to the fact the acidic engine gases leak through piston rings and can thereby contaminate ~
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the crankcase lubricant. The dispersancy and detergency additives prevent corrosion and rust on the bearings and are necessary adjuncts to the base stock by neutralizing, dis-, solving and dispersing these contaminants as well as degrada-,; ' , .
tion products from fluid oxidation.

The following examples are illustrative of various 1 lubricant compositions incorporating ester-oligomer base sl stocks. All parts and percentages are by weight, unless other~

l wise noted.
~J Example 1 A lubricant blend having the following composition was prepared and subjected to the Coordinating Research Coucil Council's (CRC) L-38 test, also known as Method 3405 of Federal -~ ;
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Test Method Standard Number 791a.
LUBRICANT COMPOSITION ~ j-Component %
Hydrogenated mixed decene trimers and tetramers ................ 40 -Trimethylolpropane triheptanoate ............................... 40 Methacrylate vinyl pyrrolidone copolymer ...................... 9.5 Lubrizol 3826A (blend of zinc dialkyldithiophosphate, overbased calcium alkylbenzene sulfonate, over -;
based calcium phenate, and succinimide) ................... 10.0 Phenyl-alpha-naphthylamine .................................... 0.5 Benzotriazole ~ 0.02 Silicone Antifoam ~ 25 ppm ', .
The CRC L-38 test is designed to evaluate crankcase lubricating oils for resistance to oxidation, corrosion, sludge and varnish, when subjected to high temperature opera-tion.
The procedure involves the continuous operation of a single cylinder CLR oil evaluation engine under constant speed, air fuel ratio and uel flow conditions fox a total of 40 hrs., subsequent to a breaking period of 4-l/2 hours. Prior to each run, the engine is thoroughly cleaned, pertinent measurements of engine parts are taken, and a new piston, piston rings and new copper-lead connecting rod bearing inserts are installed.
The key operating conditions of the engine of this evaluation are as ollows:
Duration .......................... 40 hours Speed ............................. 3150 + 25 RPM
Load .............................. Adjusted to pro-vide proper fuel ` 30 flow at specified air-fuel ratio Fuel Flow ......................... 4.75 ~ 0.25 lbs./hr.

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Air-Fuel Ratio ...................... ~ 14.0 ~ 0.5 Jacket Out Temperature .............. ..200 + 2F.
Difference between jacket in ;~ ;
and jacket out temperature ....... ..10 + 1 F . : :
Gallery oil temperature ............. ..290 + 2F. ~ ~

At the conclusion of the run, the engine is dis- ~ -,: .
assembled and the performance of the oil is judged by a visual `~
examination o~ the engine for deposits, by the weight loss of the copper-lead bearing, and by comparison of the inspection data on samples of used oil taken at periodic intervals with `~
the inspection data on the new oil.
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Test results are tabulated below:

TEST RESULTS ~
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4 0 ~OUR CRANKCASE OIL OXIDATION EVALUATION
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Bearing Weight Loss, Mg.
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Top ............. ~................... ..16.6 Bottom .............................. ..16.7 Total ............................... ..33.3 A maximum of 40 milligrams (mg.) weight loss is -allowed for this test. This test imposes severe corrosion conditions upon the copper-lead connecting rod bearing. Ordi~
narlly with ester based lubrlcants, i.e., wherein an ester is the base stock, test failure will occur as manifested by a :,, j .
; bearing weight loss in excess of the maximum 40 mg. allowed.

The test resul~ of 33.3 mg. weight loss is considered acceptable and indicative of a fluid that will not cause ex-;i cessive bearing corrosion in actual engine operation.
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This is a visuàl cleanliness inspection wherein a rating of O to 10.0 is given~ A rating of 10.0 is clean. Varnish is indioative of the degra~ation tendency of the lubricant, and is manif~sted by a shellac-like glaze that has formed along the metal part~ii.
Varnish De~osit Rating Slud~Deposit Ratin~
Piston Skirt~O~ 9,8 Rocker Arms.............. ,.~....................... 9.9 Rocker Ar~ Cover...... 9.9 . Rocker Arm coverO ~ .............. .9.~
10 . Push Rod Cover................... g.9 Push Rod Co~er....... ~.. .9.9 Cylinder Wall, BRT............ 9.9 Oil Screen... O....... O.. lO.o. Oil Pan.. O.................... 9.9 Oil Pan. r~ 9~9 Crankcase Cover plate 9.9 Crankcase Cover Plate.. ...9.9 ~ Yarnish Total.......... 59.~ Sludge Total~......... ,.,59,5 ~ OIL ~YLSIS~
~ew Oil Usea Oil, Hours 0 20. ~ 40 ~ .
~ Neutraliza~ion ~o......... . 1.87 2.gQ 3.22 3.57 3.~6 .~; .
Viscosity-SUS at 100F..... ~62.4 344.9 ~1.4 334.0 33Q.5 at 210F..... ~ 75.89 73~16 71.47 70040 69.57 . Stripped Viscosity at 210F.......... 71.55 Viscosity Increase at 100F. 4.8 5.8 7.8 8.8 .a~ 210F~ ~o6 5.8 7.2 8.3 Oil Consumption~ lb/hr~ O~ 0-10 hour5 0~000 :~ ' 25 10~20 hours 0.015 20-~0 hours 0~004 ~0-40 hours 0.013 0-4Q hours --/2 ^

44~ ~501.,~1~514 Ex A lubricant blend identical to the ~ormulation o~
Exam~le 1 was subjec~ed to a severe wear and high temperatur~
test run at high speed on a 1970 Oldsmobile, 8 cylindery 425 .
c~bic inch engine. The duration of the test was 64 hours an~
the criteria for a test pass is that the viscosity at 40 hours be less than a 40~0 increi3se~ a~d that the cam plus li~ter wear be less than .002~ maximum, and les~ than .001" average wear.
This test is called the 1970 General Motors "MS" Lubricant Eva1ua~ion: Sequence II~C. A su~mary of the engine test results appears below:

Hour ViscositY Cha~e Percent ~ew 72. 66 o 68. o8 68. 72 0. 64 -~ol 6 69~ 66 1. 58 ~02 3, 24 71.79 ~71 ~5 ...
2 71~.60 6.52 ~10 : 20 40 76. o7 7~ 99 ~12 . `i . .
48 77. 44 9. 36 ~14

5~ 80. 61 12. 53 *~8 . ,1 . . , , 64 82. 17 14. o9 -~21 ~
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Comment: The 1 ~ increase in viscosity ater 40 hours is indi-2~ cative of excellent 1uid stability. The maximum allowed is 40~.
-- Sludge Rating: Front Cover Deflector 906 (10.0 is clean~
Rocker Cover-R 9.5 Rocker Cover-~ 9.5 3o Rocker Cover Baffle-R 9.6 501/45~4 Z~
Aver~ge g.6 . Oil Screen Plugging (%) o Varnish Rating: Piston Skirts (10.0 is clean) Thrust 9.6 Anti-Thrus~ 9~6 Average 9.6 .
Sludge and varnish deposits in ~he critical area~
noted wexe of very low magnitude for the severe type o operating conditio~s imposed by this test. In compari50n; mineral oil based llibricarlts woul~ have a tendency to f~rm much heavier . .
~ slud~e and varnish deposits under equivalent conditions.
: Oil Ring Land Faces Rating:
., , A~ove . 5. 9 : ., .
,! . 15 Below 8.3 `. Average 7. 0 Wear: ~ Cam plus liter (in. ) ~laximum 0. OOl ~i ~inimum . o.. 0003 ~verage 0. 0007 P.os~! Bear~n~ T.AJt.. l.~ m,.-r~
Rod ~fulnber 4 5~.1 Rod l~umber 5 ~ 65.1 Average 59. 1 ~umber Nurnber ~u~iber Scuffed and/or Worn:Scuffed Worn Scuffed ~ Worn Cam Lobes 0 0 0 Lifters o o . o - Valve Stem Tips 4 2 8 .~ .
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l~qZ07 Rocker Arm Pads 3 2 5 Rocker Arm Pivots 3 3 10 Oil Consumption: (Qt.) 4.53 ~ Ring Area:
; Oil Ring Plugging (%) 0 Number Stuck Rings None Number Sluggish Rings None i:
Number Stuck I,ifters: None Comment: Inspection of the seal showed them to be in good . ~ . , condition, with no evidence of degradation. The seals re-tained their pliability and dimensional integrity, and no leakage was evident.
Example 3 ,-~ , !'~ . A lubricant blend identical to that tested in Ex-ample 1 was evaluated in a test method designed to relate particularly to short trip service under typical winter con-ditions in the upper Mid-Western U.S. The conditions of this ~1 ~.. `:.
test are most useful in evaluating the rusting characteristics of motor oils due to the fact that test conditions encourage 20 rust formation in critical parts of the engine. This test is called the~1971 General Motors Lubricant Evaluation:
Sequence IIC, and is conducted in a 1971 Oldsmobi~e with an 8 cylinder, 425 cubic inch engine.
Prior to each test run, the engine is completely ;
disassembled, solventcleaned, measured, and rebuilt in strict ~-accordance to furnished specifications. Following the pre- -paration, the engine is installed on a dynamometer test stand equipped with the appropriate accessories for controlling speed, load, temperatures, and other various engine operating -~ :

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conditions. The engine is operated continuously for 28 hours under conditions of moderate engine speed, partially warmed-up -~ -jacket co~lant temperature, and rich air-fuel ratio. The \ following is a summary of test operating conditions:
Speed, revolutions per minute trpm) 1500 - 20 Load, brake horsepower (bhp) 25 + 2 Oil, to engine, after filter, deg. F. 120 - 2 Oil pump outlet, psi 50 ~ 10 Coolank, jacket out, deg. F. 110 - l Coolant, jacket in, deg. F.105 - l Coolant, jacket flow rate, gpm 60 - 1 Coolant, crossover out, deg. F 109 + 2 a-t at gpm 3.0 _ 5 Coolant, crossover pressure outlet, +
psi 2.5 - 0.5 Coolant, breather tube out, deg. F. 60 ++ 2 at ~ at gpm 3.0 0.5 - Coolant, rocker covers out, deg. F. 60 ++ 2 at at gpm per cover 1.5 - 0.5 Coolant out, rocker cover pressure +
psi 13.0 - 0.5 Air-Fuel ratio 5.0 - 0.5 Carburetor, air temperature, deg. F. 80 - 2 - Carburetor, air humidity, grains per lb. of dry air 80 - 5 Carburetor, pressure,in. water 0.1 to 0.3 Bowlby rate, cfm at 100 E'.. and +
29.7 in EIg 0.8 - 0.1 Intake manifold vacuum, in Hg~ 18 - 1.5 Exhaust back pressure~ in. water 4 - l ~,` .

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( C-444~/4501/~514 Exhaust back pressure max. differentialJ
in water Q.2 Crankcase oil filler tube Removed and plug~ed .

Immediately following this 28-hour perio~ o~ opera~ion, the e~gine is operated ~or 2 hours under the same c~ditions as ` abo~e, excep~ ~or the following changes:
Coolant, jac~e~ out, deg. F. 120 + 1 , Coolant, jacket in~ deg. F. 115 ~ 1 : Coolant,~ cr~ssover out, degr F. 119 ~ 2 . The engine is then shut down for 30 minute~ to change ~:
the carburetor, perform an oiL level check, :chan~e the spark plugs, and to make adjustments to the rocker cover coolant system~
Following this shutdown and without oil drain the engine is opexated for 2 hours under the following hot conditions.
`: ~5 Speed, rpm 3600 20 , . .
-' . Load, bhp IOO ~ 2 ., ~ , Oil, into engine, after . filter, all visco~ities, ~
deg. F..................... 260 - 2 20Coolant, jacket out, deg. F.200 ~ 2 jacket in,deg. F. 190 + 2 : jacket flow rate, gpm................ 60 + 1 intake crossover +
out, deg. Fo~ 197 - 2 Breather tube out, deg. F.
; at gpm............. ~.0 - 0.5 Rocker covex o~t, deg~ F. 198 ~ 2 at at gpm pex cover 1~5 - 0,5 30 Rocker cover pressure~ psi 5.0 - 0.5 Air-Fuel rati~-- - 16~5 ~ 0~5 ` ~7 ~, , -444~ ~sOl/4~14 Carburetor~ air temperature, deg. F 80 -- 2 air humidity~ grains per lb. of dry air 80 - 5 pressure, in. water O,l to 0.3 slowby rate, cfm at lOO deg. F and 29.7 in ~g. . 2.2 + 0.2 Intake manifola vacuum, in. Hg. 11 - 2. 5 Exhaust back pressure, in. water . 30 + ~
Crankcase oil filler tube removed and plugged . I~SPECTIO~
On completion of the test, the engine is completely disasse~b1ed an~ inspected for rusting using the appropriate Coord~natlng Research Council (CRC) rating ~echniques, A rating.
~' of 10. 0 is clean. Parts rated are indicated below:
;, 15 ( 1 ) Rust - (CRC ~ Manual ~o. 7. Engine rust rating is the a~erage o~ five parts listed below: ;
Valve lifker bodies Valve lifter plungers Valve lifter balls Oil pump xelief valve Push rod~
: : (2) Others. Oil pump relief valve stic'~ing and valve lifter plunger sticking.

2~ SIJMM~R~ OF E~GI~E: TEST RESIJLTS
E,ifter Bodies 8. 9 ( 10. 0 is clean ) 7 Plungers 8. 6 Balls 8.,6 ~o Relief Valve Plunger 8.8 _ 18 -l~Z~
Push Rods 8.0 Average 8.6 Stuck Lifters: (number) None ' ~ ~
Stuck Relief Valve: No ~;
, Oil Consumption: (qts.) 0.25 Comment: An 8.4 average rust rating is considered acceptable `
in this severe rust promoting test. The 8.6 average rust ~
obtained by the test is especially signiicant with reyard to -;
the lifter bodies, plungers, balls and relief valve plunger due ~o the fact that the aforesaid parts function within close tolerance restrictions. ~"
Inspection of the seals showed them to be in good ;-` :
condition, with no evidence of degradation. The seals retained ;`
f their pliahility and dimensional integrity and no leakage was evident. The results of this test are indicative of a crank-, case lubricant which has surpassed severe wear and temperature conditions. `
Example 4 -~
A lubricant blend identical to the formulation of '~
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Example 1 was subjected to the Ford Sequence VC Test. This test is designed to evaluate the lubricant's ability to control and disperse harmful contaminants, such as acidic blowby gases, particulate carbon, highly oxygenated oxidation products, and the like. These contaminants cause sludge and varnish deposits `
that are most likely to occur when the engine is subjected ~ ;
to various intermittent operating cycles which include idling, medium speed operation, high speed operation and shutdown.
The Ford Sequence yc Test is conducted on a Ford, 8 cylinder, 302 cubic inch engine. In brief, it consists of four -- 1 9 ~

~ 2~
consecutive operating cycles ~ each having a duxation of four hours. In each cycle the engine iS subjected to separate periods of idling, medium speed operation and high speed ;
operation.
After the operating sequence of 4 cycles is completed, the engine is shut down ~or 8 hours, after which ~-the entire operation is repeated. The test lasts for a total of 192 hours of operation.
On completion of the test, the engine is completely disassembled, inspected and xated. ~ summary of the results .
is as follows: ~;

Results ~ .
A rating of 10.0 is clean -Average Sludge Rating ................. 9.09 (8.5 passes) Piston Skirt Varnish Rating ........... 8.16 (7.9 passes) ;

Average Varnish Rating ....... ~........ 8.93 ~` (8.0 passes) ;
; 20 Comment: The results evidence the lubricant's ability to disperse harmful contaminants and maintain the engine in a clean operating condition, thereby assuring good performance `~
under severe operating condltions. Inspection of the seals showed them to be in good condition, with no evidence of degradation~ The seal retained their pliability and dimensional integrity - no leakage was evidenced.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A base stock composition suitable for use in a crankcase lubricant comprising an effective amount of a blend of a liquid polyol ester and a component selected from the group of a liquid hydrogenated poly-alpha-olefin and a liquid hydrogenated alpha-olefin oligomer wherein the olefin has a carbon chain length of about 6 to 14 carbon atoms, where-in said polyol ester is the reaction product of an aliphatic monocarboxylic acid having a carbon length of about 4 to 12 carbon atoms, with an aliphatic polyol having at least two methylol groups on a quaternary carbon atoms, the ratio of ester to olefin varying from about 35:65 to about 80:20 parts by weight and said blend imparting an elastomer seal swell ranging from about 4% to about 20% and having a viscosity at 210°F. of from about 3 centistokes to about 20 centistokes.

2. The composition of Claim 1, wherein said polyols are formed from ether condensation of two or more polyols, pro-vided that no more than four polyol units are so condensed and further provided that at least four OH groups are available.

3. The composition of Claim 1, wherein the ratio of polyol ester to poly-alpha-olefin is from about 40:60 to about 66.7:33.3 parts by weight.

4. The composition of Claim 1 wherein said polyols are selected from the group consisting of trimethylolpropane, trimethylolethane, neopentyl glycol, pentaerythritol, 2-butyl-2-ethyl-1,3-propanediol, 2,2,4-trimethyl-1,3 pentanediol, and mixtures thereof.

5. The composition of Claim 4 wherein said polyols are selected from the group consisting of trimethylolpropane trimethylolethane, pentaerythritol, and mixtures thereof.

6. The composition of Claim 1, wherein said polyol ester is a trimethylolpropane triester.

7. The composition of Claim 1, wherein said polyol is selected from the group consisting of ditrimethylolethane, ditrimethylolpropane, dipentaerythritol, tripentaerythritol, and mixtures thereof.

8. The composition of Claim 1, wherein said polyol ester is a ditrimethylolpropane tetraester.

9. The composition of Claim 1, wherein said base stock contains an additive package including additives which impart anti-corrosion properties, anti-wear properties, lubricity, viscosity index-improving properties, detergency, dispersancy, metal deactivation and antifoaming properties.

10. The composition of Claim 1, wherein minor amounts of a dibasic acid are included therein.

11. A method for lubricating an automotive crankcase which comprises applying to said engine as a lubricating agent an effective amount of a blend of a liquid polyol ester and.
a component selected from the group of a liquid hydrogenated poly-alpha-olefin and liquid hydrogenated alpha-olefin oligomer wherein the olefin has a carbon chain length of about 6 to 14 carbon atoms, wherein said polyol ester is the reaction product of an aliphatic monocarboxylic acid having a carbon chain length of about 4 to 12 carbon atoms, with an aliphatic polyol having at least two methylol groups on a quaternary.
carbon atom; and wherein said blend is capable of imparting an elastomer seal swell ranging from about 4% to about 20%, and a viscosity at 210 F. of from about 3 centistokes to about 20 centistokes and wherein the ratio of ester to olefin varies from 35:65 to about 80:20 parts by weight.