Method for improving thermal-oxidative stability and elastomer compatibility

A lubricating oil comprising a lubricating oil base stock;

• wherein the lubricating oil base stock comprises a multi-aromatic base stock of the formula:
• R1—R2—(X—R2)n—R1
• wherein each R1 is the same or different and is a terminal group, each R2 is the same or different and represents a substituted or unsubstituted aromatic moiety;
• each X is a linking moiety that is carbon-carbon single bond or a linking group, n is a number from 1 to 2000, and the ratio of the total number of aromatic ring carbon atoms to aliphatic carbon atoms in said formula is greater than 0.32:1;
• wherein the multi-aromatic base stock has a kinematic viscosity greater than 20 mm2/s at 100° C.;
• and wherein, in an apparatus lubricated with said lubricating oil, thermo-oxidative stability and elastomer compatibility are improved as compared to thermo-oxidative stability and elastomer compatibility achieved using a lubricating oil base stock other than the multi-aromatic base stock.

A multi-aromatic base stock of the formula:

• R1—R2—(X—R2)n—R1
• wherein each R1 is the same or different and is a terminal group, each R2 is the same or different and represents a substituted or unsubstituted aromatic moiety;
• each X is a linking moiety that is carbon-carbon single bond or a linking group, n is a number from 1 to 2000, and the ratio of the total number of aromatic ring carbon atoms to aliphatic carbon atoms in said formula is greater than 0.32:1;
• wherein the multi-aromatic base stock has a kinematic viscosity greater than 20 mm2/s at 100° C.;
• and wherein, in an apparatus lubricated with a lubricating oil comprising said multi-aromatic base stock, thermo-oxidative stability and elastomer compatibility are improved as compared to thermo-oxidative stability and elastomer compatibility achieved using a lubricating oil base stock other than the multi-aromatic base stock.