Durable lubricating fluids for electric vehicles

1. A durable lubricating composition for electric or hybrid-electric vehicles, the lubricating composition comprising:

a base oil of lubricating viscosity;

at least about 0.7 weight percent of a thiadiazole or derivative thereof,

an amine salt of a phosphoric acid ester providing at least about 100 ppm of phosphorus to the durable lubricating composition;

a sulfur plus phosphorus to nitrogen ((S+P)/N) weight ratio of at least 2.3;

the lubricating composition having at least about 150 ppm of phosphorus and at least about 2000 ppm of sulfur; and

a conductivity durability of about 50,000 pS/m or less.

2. The durable lubricating composition for electric or hybrid-electric vehicles of claim 1 , wherein the thiadiazole is selected from a mono hydrocarbyl thiol-substituted thiadiazole, a bishydrocarbyl thiol-substituted thiadiazole, or combinations thereof.

3. The durable lubricating composition for electric or hybrid-electric vehicles of claim 1 , wherein the thiadiazole is 1,3,4-thiadiazole or derivative thereof.

4. The durable lubricating composition for electric or hybrid-electric vehicles of claim 1 , wherein the thiadiazole provides at least about 2000 ppm sulfur to the durable lubricating composition.

5. The durable lubricating composition for electric or hybrid-electric vehicles of claim 4 , wherein the durable lubricating composition includes up to about 3500 ppm total sulfur and up to about 300 ppm total phosphorus.

6. The durable lubricating composition for electric or hybrid-electric vehicles of claim 1 , wherein the lubricating composition includes about 1 weight percent or less of the thiadiazole or derivative thereof.

7. The durable lubricating composition for electric or hybrid-electric vehicles of claim 1 , wherein the thiadiazole or derivative thereof includes one or more compounds having a structure of Formula I:

wherein

Each R 1 is independently hydrogen or sulfur;

Each R 2 is independently an alkyl group;

n is an integer of 0 or 1 and if R 1 is hydrogen then the integer n of the adjacent R 2 moiety is 0 and if R 1 is sulfur then the n of the adjacent R 2 moiety is 1; and

wherein at least one R 1 is sulfur.

8. The durable lubricating composition for electric or hybrid-electric vehicles of claim 1 , wherein the amine salt of a phosphoric acid ester includes one or more of a monoalkyl phosphoric acid ester and/or a dialkyl phosphoric acid esters and wherein the alkyl groups thereof may be linear or branched.

9. The durable lubricating composition for electric or hybrid-electric vehicles of claim 7 , wherein the amine salt of a phosphoric acid ester is represented by Formula II

wherein

R 3 and R 4 may be independently hydrogen or a linear, branched, or cyclic hydrocarbyl group;

m is an integer from 0 to 1, p is an integer from 1 to 2, and m+p equals 2;

R 5 , R 6 , R 7 and R 8 may be independently hydrogen or a hydrocarbyl group and at least one of R 5 to R 8 is a hydrocarbyl group.

10. The durable lubricating composition for electric or hybrid-electric vehicles of claim 9 , wherein R 3 and R 4 may independently be a C3 to C10 alkyl group.

11. The durable lubricating composition for electric or hybrid-electric vehicles of claim 10 , wherein at least one of R 5 , R 6 , R 7 and R 8 is C10 to C20 alkyl group.

12. The durable lubricating composition for electric or hybrid-electric vehicles of claim 10 , wherein two of R 5 , R 6 , R 7 and R 8 are independently a C10 to C20 alkyl group.

13. The durable lubricating composition for electric or hybrid-electric vehicles of claim 1 , wherein the amine salt of a phosphoric acid ester provides about 40 to about 90 weight % of the total phosphorus in the durable lubricating composition.

14. The durable lubricating composition for electric or hybrid-electric vehicles of claim 13 , wherein the thiadiazole or derivative thereof provides at least about 99 weight % of the total sulfur in the durable lubricating composition.

15. The durable lubricating composition fur electric or hybrid-electric vehicles of claim 1 , wherein the lubricating composition includes about 0.25 to about 0.5 weight percent of the amine salt of a phosphoric acid ester.

16. The durable lubricating composition for electric or hybrid-electric vehicles of claim 1 , wherein the lubricating composition has an initial conductivity before aging of about 150,000 or less when measured according to ASTM D2624-15 at 1.5 volts, 20 Hz, and at 160 C.

17. The durable lubricating composition for electric or hybrid-electric vehicles of claim 1 , wherein the conductivity durability is the difference between an initial conductivity and a final conductivity, and the initial and final conductivities are measured according to ATSM D2624-15 at 1.5 volts, 20 Hz, and at 160 C, and wherein the final conductivity is measured after the lubricating composition has been aged according to CEC L-48-A-00 at 170° C. for 192 hours.