Oil-soluble zinc cyclic hydrocarbyl dithiophosphate-succinimide complex and lubricating oil compositions containing same

Oil-insoluble zinc salts of cyclic dithiophosphates are rendered oil soluble when combined to form a complex with alkenyl or alkyl mono- or bis-succinimides. Oil compositions containing this combination are useful as crankcase lubricants.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a combination of an oil-soluble zinc cyclic 
hydrocarbyl dithiophosphate and an alkenyl or alkyl succinimide and the 
use of said combination in lubricating oils employed for crankcase 
lubrication of internal combustion engines. 
2. Description of the Prior Art 
Metal dihydrocarbyl dithiophosphates are useful for a variety of purposes 
known in the art. The zinc hydrocarbyl dithiophosphates in particular are 
employed as oxidation and corrosion inhibitors in lubricating oil 
compositions. U.S. Pat. No. 3,089,850 teaches the preparation of metal 
cyclic hydrocarbyl dithiophosphates prepared by reacting a glycol with 
phosphorus pentasulfide followed by reaction with a basic metal compound. 
There is a problem, however, with certain of the metal cyclic hydrocarbyl 
dithiophosphates of this reference in that they are essentially insoluble 
in lubricating oil formulations. 
Thus, the insolubility and resulting essential nonuse of certain metal 
cyclic hydrocarbyl dithiophosphates is a severe drawback in the utility of 
these compounds in crankcase lubricants. 
SUMMARY OF THE INVENTION 
It has now been found that an oil-insoluble zinc cyclic hydrocarbyl 
dithiophosphate may be made oil soluble by forming a complex between the 
dithiophosphate and an alkenyl or alkyl mono- or bis-succinimide. 
Thus, this invention relates to a lubricating oil composition comprising a 
major amount of an oil of lubricating viscosity and a minor proportion 
sufficient to inhibit oxidation and corrosion of a complex prepared by 
reacting: 
(a) a zinc salt of a hydrocarbyl dithiophosphoric acid of the formula: 
##STR1## 
wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are the 
same or different and each is hydrogen or alkyl of 1 to 3 carbon atoms 
with the proviso that each of R.sub.1 through R.sub.6 cannot all be 
hydrogen at the same time; with 
(b) an oil-soluble alkenyl or alkyl mono- or bis-succinimide of the 
formula: 
##STR2## 
wherein X is amino or a group of the formula: 
##STR3## 
R.sub.7 is an alkenyl or alkyl group containing from about 20 to 300 carbon 
atoms; U is alkylene containing 2 to 6 carbon atoms; and n is an integer 
of from 0 to 6; 
wherein the weight ratio of (b) to (a) is in the range of 3:1 to 25:1, 
preferably 3:1 to 10:1. 
DETAILED DESCRIPTION 
The cyclic hydrocarbyl zinc dithiophosphates useful in the present 
invention are zinc salts of cyclic hydrocarbyl dithiophosphoric acids 
represented generally by the formula: 
##STR4## 
wherein R.sub.1 through R.sub.6 are defined above. 
These compounds can be prepared by the reaction of a suitable glycol or 
mixture of glycols with phosphorus pentasulfide followed by reaction with 
a basic zinc compound. Methods to prepare these compounds are described in 
U.S. Pat. No. 3,089,850, and the disclosures thereof are incorporated 
herein by reference. Generally, according to this reference, cyclic 
hydrocarbyl dithiophosphoric acids are first prepared by reacting a glycol 
of the Formula II: 
##STR5## 
wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are as 
defined above, with phosphorus pentasulfide followed by reaction with a 
basic zinc compound. The reaction for preparation of the dithiophosphoric 
acid is carried out at a temperature in the range of 25.degree. C. to 
100.degree. C., optionally in the presence of a solvent and at a mole 
ratio of glycol to phosphorus pentasulfide of 2:1. 
For example, the cyclic hydrocarbyl dithiophosphoric acid may be prepared 
at a mole ratio of glycol to phosphorus pentasulfide of 2:1 by slowly and 
steadily adding the glycol (2 moles) to a toluene solution (about 600 ml) 
of the phosphorus pentasulfide (1 mole) at a temperature of from 
40.degree. C. to 113.degree. C. 
Representative of the glycols used to prepare the cyclic hydrocarbyl 
dithiophosphoric acid include 2,2-dimethyl-1,3-propanediol; 
2-ethyl-2-methyl-1,3-propanediol; 2,2-diethyl-1,3-propanediol; 
2-butyl-2-ethyl-1,3-propanediol; 2-ethyl-1,3-hexanediol; 2,4-pentanediol; 
2,2,4-trimethyl-1,3-pentanediol; 5-methyl-2,4-hexanediol; and the like. 
Because of the proviso in the definition of R.sub.1 through R.sub.6, the 
1,3-propanediol is specifically excluded. 
The basic zinc compounds which are useful in this invention include those 
zinc salts which are capable of reacting with the dithiophosphoric acids 
such as zinc oxide, zinc hydroxide, zinc carbonate, zinc propylate, and 
the like. 
The oil-soluble alkenyl or alkyl mono- or bis-succinimides which are 
employed in the additive combination of this invention are generally known 
as lubricating oil detergents and are described in U.S. Pat. Nos. 
2,992,708; 3,018,291; 3,024,237, 3,100,673; 3,219,666; 3,172,892; and 
3,272,746, the disclosures of which are incorporated by reference. These 
materials are prepared by reacting an alkenyl or alkyl-substituted 
succinic anhydride of the formula: 
##STR6## 
wherein R.sub.7 is defined above, with a polyalkylene polyamine of the 
formula: 
EQU H.sub.2 N--UNH).sub.n UNH.sub.2 
wherein U and n are defined above. 
The alkylene group designated by U, which contains from 2 to 6 carbon 
atoms, may be straight chained or branched, but will usually be straight 
chained. Illustrative alkylene groups are ethylene, propylene, 
1,2-propylene, tetramethylene, hexamethylene, etc. The preferred alkylene 
groups are from two to three carbon atoms, there being two carbon atoms 
between the nitrogen atoms. 
Non-limiting examples of suitable amino compounds include: 
1,2-diaminoethane; 1,3-diaminopropane; 1,4-diaminobutane; 
1,6-diaminohexane; diethylene triamine; triethylene tetramine; 
tetraethylene pentamine; 1,2-propylene diamine; and the like. 
A product comprising predominantly mono- or bis-succinimide can be prepared 
by controlling the molar ratios of the reactants. Thus, for example, if 1 
mole of amine is reacted with 1 mole of the alkenyl or alkyl substituted 
succinic anhydride, a predominantly mono-succinimide product will be 
prepared. If 2 moles of the succinic anhydride are reacted per mole of 
polyamine, a bis-succinimide will be prepared. 
The preparation of the alkenyl substituted succinic anhydride by reaction 
with a polyolefin and maleic anhydride has been described, e.g., U.S. Pat. 
Nos. 3,018,250 and 3,024,195. Reduction of the alkenyl substituted 
succinic anhydride yields the corresponding alkyl derivative. Polyolefin 
polymers for reaction with the maleic anhydride are polymers comprising a 
major amount of C.sub.2 to C.sub.5 mono-olefin, e.g., ethylene, propylene, 
butylene, isobutylene and pentene. The polymers can be homopolymers such 
as polyisobutylene as well as copolymers of two or more such olefins such 
as copolymers of: ethylene and propylene; butylene and isobutylene; etc. 
Other copolymers include those in which a minor amount of the copolymer 
monomers, e.g., 1 to 20 mole percent is a C.sub.4 to C.sub.8 nonconjugated 
diolefin, e.g., a copolymer of isobutylene and butadiene or a copolymer of 
ethylene, propylene and 1,4-hexadiene; etc. 
The olefin polymers contain from about 20 to 300 carbon atoms and 
preferably from 30 to 150 carbon atoms. An especially preferred polyolefin 
is polyisobutylene. 
The lubricating oils of this invention contain an oil of lubricating 
viscosity and a complex which provides from about 5 to 30 millimoles/kg 
and preferably from 18 to 24 millimoles/kg of the oil-insoluble zinc 
cyclic hydrocarbyl dithiophosphates and from 1 to 15 weight percent and 
preferably from 3 to 8 weight percent of the alkenyl or alkyl succinimide. 
The complex, the exact structure of which is not known, may be formed by 
reacting the zinc cyclic hydrocarbyl dithiophosphate and the succinimide 
together in a diluent in which both reactants are soluble. For example, 
the reactants may be combined in the proper ratio in a solvent such as 
toluene or chloroform, the solvent stripped off, and the complex thus 
formed may be added to the oil or the oil may be added prior to solvent 
stripping, i.e., the oil is added to the solvent-complex solution and the 
solvent subsequently stripped. 
The diluent is preferably inert to the reactants and products formed and is 
used in an amount sufficient to insure solubility of the reactants and to 
enable the mixture to be efficiently stirred. 
Temperatures for preparing the complex may be in the range of from 
25.degree. C. to 200.degree. C. and preferably 25.degree. C. to 80.degree. 
C. Since the zinc cyclic hydrocarbyl dithiophosphates are essentially 
insoluble in oil, the complex may not be made in-situ in the oil, e.g., 
addition of the insoluble zinc cyclic hydrocarbyl dithiophosphate to an 
oil containing the appropriate ratio of a succinimide does not solubilize 
the dithiophosphate. 
Alternately, the soluble cyclic hydrocarbyl zinc 
dithiophosphate-succinimide complexes of this invention are prepared by 
reacting the cyclic hydrocarbyl dithiophosphoric acid with the basic zinc 
compound and the oil-soluble alkenyl or alkyl mono- or bis-succinimide in 
an organic solvent. 
In carrying out this process, the cyclic hydrocarbyl dithiophosphoric acid 
is added to a slurry containing a basic zinc compound and the succinimide 
in an organic hydrocarbon solvent. The components are reacted at a 
temperature of about 25.degree. C. to 180.degree. C. A promotor such as 
water or acetic acid may also be used to assist the reaction. 
Preferably, the temperature is adjusted in order to azeotrope off any water 
formed during the course of the reaction, i.e., 80.degree. C. to 
140.degree. C. 
Typical examples of solvents which may be used include benzene, toluene, 
xylene, and the like. 
Sufficient basic zinc compound is present to essentially neutralize the 
cyclic hydrocarbyl dithiophosphoric acid and is present in the reaction 
mixture in an amount of from about 0.7 to 1.3 equivalents per equivalent 
of the cyclic hydrocarbyl dithiophosphoric acid. Preferably, the basic 
zinc compound and the cyclic hydrocarbyl dithiophosphoric acid are present 
in an equivalent amount. 
Weight percent ratios of alkenyl or alkyl mono- or bis-succinimides to zinc 
cyclic hydrocarbyl dithiophosphate in the complex in the range of 3:1 to 
25:1 and preferably from 3:1 to 10:1 should be maintained. Lesser amounts 
of the succinimide will result in haziness and precipitation of the zinc 
cyclic hydrocarbyl dithiophosphates. 
Additive concentrates are also included within the scope of this invention. 
They usually include from about 90 to 10 weight percent of an oil of 
lubricating viscosity and are normally formulated to have about 10 times 
the additive concentration that would be used in the finished lubricating 
oil composition. Usually, this will be a sufficient amount of complex to 
supply about 50 to 300 millimoles/kg of the zinc cyclic hydrocarbyl 
dithiophosphate and 10 to 150 weight percent of the alkenyl or alkyl 
succinimide. Typically, the concentrates contain sufficient diluent to 
make them easy to handle during shipping and storage. Suitable diluents 
for the concentrates include any inert diluent, preferably an oil of 
lubricating viscosity, so that the concentrate may be readily mixed with 
lubricating oils to prepare lubricating oil compositions. Suitable 
lubricating oils which can be used as diluents typically have viscosities 
in the range from about 35 to about 500 Saybolt Universal Seconds (SUS) at 
100.degree. F. (38.degree. C.), although any oil of lubricating viscosity 
can be used. 
Suitable lubricating oils which can be used to prepare a lubricating oil 
composition or concentrate are oils of lubricating viscosity derived from 
petroleum or synthetic sources. The oils can be paraffinic, naphthenic, 
halo-substituted hydrocarbons, synthetic esters, or combinations thereof. 
Oils of lubricating viscosity have viscosities in the range from 35 to 
50,000 SUS at 100.degree. F., and more usually from about 50 to 10,000 SUS 
at 100.degree. F. 
Other conventional additives which can be used in combinations with the 
additive combination of this invention include oxidation inhibitors, 
antifoam agents, viscosity index improvers, pour-point depressants, and 
the like. These include such compositions as chlorinated wax, benzyl 
disulfide, sulfurized sperm oils, sulfurized terpene, phosphorus esters 
such as trihydrocarbon phosphites, metal thiocarbamates such as zinc 
dioctyl-dithiocarbamate, polyisobutylene having an average molecular 
weight of 100,000, etc. 
The lubricating oil compositions of the invention are useful for 
lubricating internal combustion engines, automatic transmissions and as 
industrial oils such as hydraulic oils, heat-transfer oils, torque fluids, 
etc. The lubricating oils can not only lubricate the engines but, because 
of their dispersancy properties, help maintain a high degree of 
cleanliness of the lubricated parts.

The following examples are provided to illustrate the invention. It is to 
be understood that they are provided for the sake of illustration and not 
as a limitation on the scope of the invention. 
EXAMPLES 
Example 1 
To a 2-liter, 3-necked flask equipped with a stirrer, nitrogen inlet, 
dropping funnel and condenser containing 600 ml of toluene and 222 gm (1.0 
mole) of P.sub.2 S.sub.5 was added 208.3 gm (2.0 mole) of 2,4-pentanediol 
over a period of 25 minutes. The temperature rose to 43.degree. C. with a 
large volume of H.sub.2 S evolving. After stirring the reaction mixture 
under nitrogen for 0.5 hour, the reaction mixture was heated to reflux for 
about 2 hours. The reaction mixture was then filtered and the filtrate 
stripped of solvent in a Rotary Evaporator under full pump vacuum and a 
water-bath temperature up to 80.degree. C. The product, a greenish-yellow 
oily liquid, weighed 384.5 gm. Acid number of product was 249; 239 mg 
KOH/gm and .sup.31 PNMR confirmed the cyclic nature of the product having 
the formula: 
##STR7## 
In a similar manner, cyclic hydrocarbyl dithiophosphoric acids from 
neopentyl glycol and 2-ethyl-1,3-hexanediol were prepared by substituting 
an equivalent amount of the respective glycol for the 2,4-pentanediol in 
the above reaction. 
Example 2 
To a 2-liter, 3-necked flask equipped with a stirrer, nitrogen inlet, 
dropping funnel and Dean-Stark trap containing 480 ml toluene, 495 gm of 
polyisobutenyl succinimide (prepared by reacting polyisobutenyl succinic 
anhydride and triethylene-tetramine wherein the number average molecular 
weight of the polyisobutenyl was about 940 and in a mole ratio of amine to 
anhydride of 0.90) and 20.34 gm (0.25 mole) of zinc oxide at a temperature 
of 50.degree. C. was added 115 gm (0.5 mole) of the cyclic hydrocarbyl 
dithiophosphoric acid of 2,4-pentanediol of Example 1 over a period of 45 
minutes. The temperature was elevated to about 75.degree. C. and 
maintained for 3.5 hours after which the temperature was raised to reflux 
for 1.5 hours. The reaction mixture was cooled, diluted with 200 ml 
toluene, heated to 50.degree. C. and filtered. The clear filtrate was 
stripped in a Rotary Evaporator under a full pump vacuum and a water-bath 
temperature up to 82.degree. C. to yield zinc cyclic hydrocarbyl 
dithiophosphate of 2,4-pentanediol-succinimide complex. 
In a similar manner, the zinc cyclic hydrocarbyl dithiophosphate neopentyl 
glycol-succinimide complex and the zinc cyclic hydrocarbyl dithiophosphate 
of 2-ethyl-1,3-hexanediol-succinimide complex were prepared by 
substituting an equivalent amount of the cyclic hydrocarbyl 
dithiophosphoric acid of neopentyl glycol and 2-ethyl-1,3-hexanediol, 
respectively, for the cyclic hydrocarbyl dithiophosphoric acid of 
2,4-pentanediol in the above procedure. 
Example 3 
A. Dithiophosphoric Acid Of 2-Ethyl-1,3-Hexanediol 
A 5-liter, 3-necked flask equipped with a stirrer, nitrogen inlet, dropping 
funnel and condenser containing 900 ml xylene and 86 gm (0.387 mole) of 
P.sub.2 S.sub.5 was heated with stirring to 85.degree. C. under a nitrogen 
atmosphere. To the reaction mixture was added 112.5 gm (0.769 mole) 
2-ethyl-1,3-hexanediol dissolved in 1350 ml xylene over about a 7-hour 
period. The reaction mixture was heated an additional 5 hours at 
85.degree. C. and was allowed to cool for about 12 hours. The reaction 
mixture was then filtered and the filtrate stripped of solvent in a Rotary 
Evaporator under full pump vacuum and a water bath up to 85.degree. C. The 
product, a yellow liquid, weighed 189.6 gm. 
B. Zinc Salt of Dithiophosphoric Acid of 2-Ethyl-1,3-Hexanediol 
To a 1-liter, 3-necked flask equipped with a stirrer, nitrogen inlet, 
dropping funnel and condenser was added 60.9 gm (0.178 equivalent weight) 
of dithiophosphoric acid of 2-ethyl-1,3-hexanediol prepared in Step A, 
31.18 gm (0.38 equivalent weight) ZnO, 2 ml water, and 150 ml of xylene. 
To the reaction mixture which was heated to about 70.degree. C. was added 
121 gm (0.357 equivalent weight) of dithiophosphoric acid of 
2-ethyl-1,3-hexanediol in 100 ml xylene over a period of 65 minutes. 
Heating was continued for another 2 hours after which the temperature was 
lowered to 40.degree. C. and 2 ml of water and 3.1 gm ZnO was added to the 
reaction mixture. The temperature was elevated to about 70.degree. C. and 
maintained for about 5 hours. The reaction mixture was cooled and 
filtered. The filtrate was stripped in a Rotary Evaporator under full pump 
vacuum and a water bath up to 85.degree. C. The product, a viscous yellow 
liquid weighed 197.51 gm; % Zn found, 11.21%; % P found, 11.36%. 
Example 4 
To 80 ml toluene at about 25.degree. C. were added 2.13 gm of the zinc salt 
of dithiophosphoric acid of 2-ethyl-1,3-hexanediol of Example 3-B and 6.95 
gm of polyisobutenyl succinimide (prepared by reacting polyisobutenyl 
succinic anhydride and triethylene-tetramine wherein the number average 
molecular weight of the polyisobutenyl was about 940, in a mole ratio of 
amine to anhydride of 0.90). To this clear solution was added 20 gm of oil 
(RPM 130N/480N) and the toluene was stripped off under vacuum. 
A formulated oil blend was prepared from this oil concentrate containing 
the oil-soluble complex of this invention (sufficient to supply 18 
mmoles/kg of the zinc salt of dithiophosphoric acid of 
2-ethyl-1,3-hexanediol and 3.5% of the polyisobutenyl succinimide) by 
adding to the concentrate 1.54 gm (30 mmoles/kg) magnesium sulfonate, 1.72 
gm (20 mmoles/kg) of a calcium phenate and 13 gm (6.5%) of 
polymethacrylate V.I. improver and sufficient oil to bring the total 
composition up to 200 gm. The oil blend thus prepared was bright and 
clear. The zinc salt of dithiophosphoric and 2-ethyl-1,3-hexanediol above 
was not appreciably soluble in the oil. 
Example 5 
Various oil blends were prepared as indicated in Table 1 using Mid 
Continental Parrafic base oil (CC100N) and containing several of the zinc 
cyclic hydrocarbyl dithiophosphates alone and the corresponding zinc 
cyclic hydrocarbyl dithiophosphate-polyisobutenyl succinimide complexes of 
Examples 2 and 3. 
TABLE 1 
______________________________________ 
Amount 
Component (based on % Zn) 
Observation 
______________________________________ 
zinc cyclic hydrocarbyl 
3 mmoles/kg solids 
dithiophosphate of present in 
2,4-pentanediol oil 
zinc cyclic hydrocarbyl 
3 mmoles/kg solids 
dithiophosphate of present in 
neopentyl glycol oil 
zinc cyclic hydrocarbyl 
3 mmoles/kg solids 
dithiophosphate of present in 
2-ethyl-1,3-hexanediol oil 
zinc cyclic hydrocarbyl 
18 mmoles/kg bright and 
dithophosphate of 2,4- clear oil 
pentanediol-polyisobutenyl solution 
succinimide of triethylene- 
tetramine (3.5%) complex 
zinc cyclic hydrocarbyl 
18 mmoles/kg bright and 
dithiophosphate of neopentyl clear oil 
glycol-polyisobutenyl solution 
succinimide of triethylene- 
tetramine (3.5%) complex 
zinc cyclic hydrocarbyl 
18 mmoles/kg bright and 
dithiophosphate of clear oil 
2-ethyl-1,3-hexanediol- solution 
polyisobutylene succinimide 
of triethylene-tetramine 
(3.5%) complex* 
______________________________________ 
*The zinc salt of dithiophosphoric acid of 2ethyl-1,3-hexanediol and the 
succinimide were first dissolved in toluene and after formation of the 
complex, the oil was added with subsequent removal of the toluene. 
Example 6 
Formulated oils containing the additives shown in Table 2 were prepared and 
tested in a Sequence III-D Test method (according to ASTM Special 
Technical Publication 315H). The compositions were prepared by adding each 
of the succinimide complexes of zinc cyclic hydrocarbyl dithiophosphates 
of 2,4-pentanediol and neopentyl glycol of Example 2 and 
2-ethyl-1,3-hexanediol of Example 4 to a formulated oil in a sufficient 
amount to supply 18 mmoles/kg Zn and 3.5% of the succinimide. 
The purpose of the test is to determine the effect of the additives on the 
oxidation rate of the oil and the cam and lifter wear in the valve train 
of an internal combustion engine at relatively high temperatures (about 
149.degree. C. bulk oil temperature during testing). 
In this test, an Oldsmobile 350 CID engine was run under the following 
conditions: 
Runs at 3,000 RPM/max run time for 64 hours and 100 lb load; 
Air/fuel* ratio=16.5/1, using * GMR Reference fuel (leaded); 
Timing=31.degree. BTDC; 
Oil temperature=300.degree. F.; 
Coolant temperature in=235.degree. F.--out 245.degree. F.; 
30" of water of back pressure on exhaust; 
Flow rate of jacket coolant=60 gal/min; 
Flow rate of rocker cover coolant=3 gal/min; 
Humidity must be kept at 80 grains of H.sub.2 O; 
Air temperature controlled equal inlet equal 80.degree. F.; 
Blowby Breather Heat exchanger at 100.degree. F. 
The effectiveness of the additive is measured after 64 hours in terms of 
camshaft and lifter wear and percent viscosity increase. 
The comparisons were made in a formulated base oil RPM 130N/480N at 85%/15% 
containing 30 mmoles/kg of a magnesium sulfonate, 20 mmoles/kg of a 
calcium phenate and 5.5% of a polymethacrylate V.I. improver. 
TABLE 2 
__________________________________________________________________________ 
Sequence III-D Test 
Cam + Lifter 
Wear .times. 10.sup.-3 In. 
Viscosity 
Viscosity 
SF Spec. 
SF Spec. 
Increase % 
Increase % 
Entry 
Formulation Max. (8) 
Avg. (4) 
at 40 hr. 
at 64 hr. 
__________________________________________________________________________ 
1 18 mmoles/kg zinc cyclic hydrocarbyl 
2.3 1.4 135 1553 
dithiophosphate of neopentyl glycol 
+ 3.5% succinimide complex 
of Example 2 
2 18 mmoles/kg zinc cyclic hydrocarbyl 
1.8 2.2 265 4236 
dithiophosphate of 2,4-pentanediol 
+ 3.5% succinimide complex 
of Example 2 
3 18 mmoles/kg zinc cyclic hydrocarbyl 
1.9 1.1 103 307 
dithiophosphate of 2-ethyl-1,3- 
hexanediol + 3.5% succinimide 
complex of Example 4 
__________________________________________________________________________ 
Example 7 
A formulated oil containing the succinimide complex of zinc cyclic 
hydrocarbyl dithiophosphate of 2,4-pentanediol of Example 2 was tested in 
a Sequence V-D Test method Phase 9-L (according to candidate test for 
ASTM). This procedure utilizes a Ford 2.3 liter four-cylinder engine. The 
test method simulates a type of severe field test service characterized by 
a combination of low speed, low temperature "stop and go" city driving and 
moderate turnpike operation. The effectiveness of the additives in the oil 
is measured in terms of the protection provided against sludge and varnish 
deposits and valve train wear. The results are indicated in Table 3. 
The comparisons were made in a formulated base oil Cit-Con 100N/Cit-Con 
200N at 55%/45% containing 30 mmoles/kg of a magnesium sulfonate, 20 
mmoles/kg of a calcium phenate and 8.5% of a polymethacrylate V.I. 
improver. The succinimide complex was present in sufficient amount to 
supply 8.1 mmoles/kg Zn and 3.5% of the succinimide. 
TABLE 3 
__________________________________________________________________________ 
Sequence V-D Test 
Cam Lobe Wear 
.times. 10.sup.-3 
Varnish 
Sludge 
SF Spec. 
SF Spec. 
SF Spec. 
SF Spec. 
Formulation Max. (2.5) 
Avg. (1.0) 
Avg. (6.6) 
Avg. (9.4) 
__________________________________________________________________________ 
8.1 mmoles/kg zinc cyclic hydrocarbyl 
1.1 0.8 6.86 9.7 
dithiophosphate of 2,4-pentanediol 
+ 3.5% succinimide complex 
of Example 2 
__________________________________________________________________________