Lubricant Composition Containing Viscosity Index Improver

A lubricant composition, comprising:

• at least about 60 percent by weight of an oil of lubricating viscosity;
• a viscosity index improving amount of about 0.001 to about 2 percent by weight of a polymer comprising from about 5 mol % to about 20 mol % structural units derived from ethylene, from about 50 mol % to about 90 mol % structural units derived from propylene, and from about 5% to about 30 mol % structural units derived from butylene;
• about 0.01 to about 20 percent by weight of a succinimide dispersant;
• and
• about 0.05 to about 5 percent by weight of a detergent comprising an overbased calcium, magnesium, or sodium sulfonate wherein the sulfonate has a total base number in the range from about 250 to about 600.