Synergistic combination of metallic and ashless rust inhibitors to yield improved rust protection and demulsibility in dispersant-containing lubricants

A lubricant composition comprising:

• (a) a major amount of a natural mineral oil or mixture thereof having an ISO 10 to 1500 viscosity grade range;
• (b) a rust inhibiting additive combination consisting essentially of from 0.2 to 0.4 wt %, of a calcium or barium alkenylaryl sulfonates and from 0.05 to 0.1 wt % of an alkenyl succinimide having alkenyl groups of from about 15 to about 30 carbon atoms;
• and
• (c) a borated polyolefin ashless dispersant in an amount ranging from about 0.2 to about 0.5 wt %, all wt % based on the total composition, the dispersant having a weight average molecular weight in the range of from about 2000 to about 2500.

A method for enhancing the antirust and demulsification properties of an industrial lubricant basestock;

• the method comprising blending in the basestock:
• (a) an effective amount of a rust inhibitor additive combination consisting essentially of a metal containing sulfonate rust inhibitor and an ashless alkenyl succinimide rust inhibitor;
• and
• (b) an ashless borated polyolefin dispersant wherein the weight ratio of dispersant to additive combination is less than 1.14.