Transmission fluid composition for improved wear protection
A transmission fluid composition contains a major amount of a lubricating oil basestock, and a minor amount of an additive package comprising: (i) a mixture comprising two or more phosphites and/or phosphates; (ii) one or more thioester compounds; (iii) one or more zinc dihydrocarbyl dithiophosphate compounds; and (iv) one or more oil-soluble or dispersible molybdenum-containing compounds. Such a transmission fluid may be used for controlling and/or reducing wear, e.g., in a manual transmission.
1. A transmission fluid composition comprising:
a major amount of a lubricating oil basestock; and
a minor amount of an additive package comprising:
(i) a mixture comprising two or more compounds of structures (I):
where groups R 1 , R 2 and R 3 are independently alkyl groups having 1 to 18 carbon atoms or alkyl groups having 1 to 18 carbon atoms where the alkyl chain is interrupted by a thioether linkage, provided that, in the mixture (i), at least some of groups R 1 , R 2 and R 3 are alkyl groups having 1 to 18 carbon atoms where the alkyl chain is interrupted by a thioether linkage;
(ii) one or more compounds of structures (II):
R 4 —S—R 5 —O—R 7
R 4 —S—R 5 —O—R 6 —S—R 7 (II)
where groups R 4 and R 7 are independently alkyl groups having 1 to 12 carbon atoms and R 5 and R 6 are independently alkyl linkages having 2 to 12 carbon atoms;
(iii) one or more zinc dihydrocarbyl dithiophosphate compounds; and
(iv) one or more oil-soluble or dispersible molybdenum-containing compounds.
2. A transmission fluid composition according to claim 1 , wherein the compounds of component (i) and component (ii) are each present in the composition in an amount from 0.1 to 2.0% by mass, based on the total mass of the composition.
3. A transmission fluid composition according to claim 1 , wherein the compounds of component (i) and component (ii) are present in the composition in a mass ratio of from 2:1 to 1:2.
4. A transmission fluid composition according to claim 1 , wherein the compounds of component (i) and component (ii) are each present in the composition in an amount from 0.1 to 0.8% by mass, based on the total mass of the composition, and in a mass ratio of from 4:3 to 3:4.
5. A transmission fluid composition according to claim 1 , wherein component (iii) is present in the composition in an amount from 0.4 to 5.0% by mass, based on the total mass of the composition.
6. A transmission fluid composition according to claim 1 , wherein component (iii) provides the composition with from 400 to 4500 parts per million by mass (ppm) of zinc, based on the total mass of the composition.
7. A transmission fluid composition according to claim 1 , wherein component (iv) is present in the composition in an amount from 0.1 to 2.0% by mass, based on the total mass of the composition.
8. A transmission fluid composition according to claim 1 , wherein component (iv) provides the composition with from 50 to 1000 parts per million by mass (ppm) of molybdenum, based on the total mass of the composition.
9. A transmission fluid composition according to claim 1 , wherein:
component (iii) is present in the composition in an amount from 1.2 to 2.5% by mass, based on the total mass of the composition, and provides the composition with from 750 to 2000 ppm of zinc, based on the total mass of the composition; and
component (iv) is present in the composition in an amount from 0.2 to 1.2% by mass, based on the total mass of the composition, and provides the composition with from 100 to 650 ppm of molybdenum, based on the total mass of the composition.
10. A transmission fluid composition according to claim 1 , wherein component (iv) comprises a molybdenum dithiocarbamate, a molybdenum dialkyldithiophosphate, a molybdenum alkyl xanthate, a molybdenum alkyl thioxanthate, or a combination thereof.
11. A transmission fluid composition according to claim 1 , wherein component (iv) comprises substantially no molybdenum dialkyldithiophosphate.
12. A transmission fluid composition according to claim 1 , wherein component (iv) is a di-nuclear or a tri-nuclear molybdenum compound.
13. A transmission fluid composition according to claim 1 , further comprising one or more ashless dispersants and a calcium-containing detergent.
14. A transmission fluid composition according to claim 1 , wherein one or more of the following are satisfied:
in a 4-ball wear test according to ASTM D4172, the composition exhibited an average wear scar after about 1 hour test duration of 0.35 mm or less;
in a 4-ball wear test according to ASTM D4172, the composition exhibited an average wear scar after about 2 hours test duration of less than 0.40 mm; and
in a 4-ball wear test according to ASTM D4172, the composition exhibited an average wear scar after about 1 hour or about 2 hours test duration that was at least 20% smaller than exhibited by the same composition except containing only two or only three of components (i), (ii), (iii), and (iv).
15. A transmission fluid composition according to claim 1 , wherein the composition consists essentially of:
from 75 to 97%, based on the weight of the composition, of a lubricating oil basestock exhibiting a kinematic viscosity at 100° C. (KV100), as measured by ASTM D445, from 2 cSt to 10 cSt; and
from 2.4 to 24%, based on the weight of the composition, of an additive package consisting essentially of:
(i) from 0.1 to 2.0% by mass, based on the total mass of the composition, of a mixture comprising two or more compounds of structures (I):
where groups R 1 , R 2 and R 3 are independently alkyl groups having 1 to 18 carbon atoms or alkyl groups having 1 to 18 carbon atoms where the alkyl chain is interrupted by a thioether linkage, provided that, in the mixture (i), at least some of groups R 1 , R 2 and R 3 are alkyl groups having 1 to 18 carbon atoms where the alkyl chain is interrupted by a thioether linkage;
(ii) from 0.1 to 2.0% by mass, based on the total mass of the composition, of one or more compounds of structures (II):
R 4 —S—R 5 —O—R 7
R 4 —S—R 5 —O—R 6 —S—R 7 (II)
where groups R 4 and R 7 are independently alkyl groups having 1 to 12 carbon atoms and R 5 and R 6 are independently alkyl linkages having 2 to 12 carbon atoms;
(iii) from 0.4 to 5.0% by mass, based on the total mass of the composition, of one or more zinc dihydrocarbyl dithiophosphate compounds;
(iv) from 0.1 to 2.0% by mass, based on the total mass of the composition, of one or more oil-soluble or dispersible molybdenum-containing compounds;
(v) optionally an ashless dispersant;
(vi) optionally one or more antioxidants;
(vii) optionally one or more corrosion inhibitors;
(viii) optionally one or more friction modifiers;
(ix) optionally a calcium-containing detergent; and
(x) optionally additional lubricating oil basestock,
wherein one or more of the following are satisfied:
the composition exhibits a zinc content of from 400 to 4500 ppm, based on the total mass of the composition;
the composition exhibits a molybdenum content of from 50 to 1000 ppm, based on the total mass of the composition; and
the composition exhibits a phosphorus content of from 400 to 5000 ppm, based on the total mass of the composition, and
wherein one or more of the following are satisfied:
in a 4-ball wear test according to ASTM D4172, the composition exhibited an average wear scar after about 1 hour test duration of 0.35 mm or less;
in a 4-ball wear test according to ASTM D4172, the composition exhibited an average wear scar after about 2 hours test duration of less than 0.40 mm; and
in a 4-ball wear test according to ASTM D4172, the composition exhibited an average wear scar after about 1 hour or about 2 hours test duration that was at least 20% smaller than exhibited by the same composition except containing only two or only three of components (i), (ii), (iii), and (iv).
16. A transmission fluid composition according to claim 15 , wherein the composition exhibits a phosphorus content of from 1000 to 2300 ppm, based on the total mass of the composition.
17. A transmission fluid composition according to claim 15 , wherein one or more of the following is satisfied:
the lubricating oil basestock is a Group II basestock, a Group III basestock, or a combination thereof;
the additive package comprises from 0.1 to 5% by mass of an ashless dispersant;
the ashless dispersant comprises a polyisobutenyl succinimide formed from polyisobutenyl succinic anhydride and a polyalkylene polyamine, wherein the polyisobutenyl group is derived from polyisobutene and exhibits a number average molecular weight (Mn) from about 750 to about 5000 Daltons;
the additive package comprises an overbased calcium-sulfonate detergent, an overbased calcium salicylate detergent, or a combination thereof, which detergent provides the transmission fluid composition with from 500 to 4500 parts per million by mass of calcium;
the additive package comprises at least two antioxidants, other than any compounds that may function as antioxidants from components (i), (ii), (iii), and (iv);
the additive package comprises one or more friction modifiers;
the additive package comprises lubricating oil basestock, in addition to the lubricating oil basestock that forms a majority of the transmission fluid composition; and
the transmission fluid composition exhibits a boron content from 15 to 180 parts per million by mass, based on the total mass of the composition.
18. A method of controlling or reducing wear in a manual transmission, the method comprising lubricating the transmission with a transmission fluid composition according to claim 1 .
19. A method of controlling or reducing wear in a manual transmission, the method comprising lubricating the transmission with a transmission fluid composition according to claim 11 .
20. A method of controlling or reducing wear in a manual transmission, the method comprising lubricating the transmission with a transmission fluid composition according to claim 14 .