My 2005 subaru impreza makes a knocking sound when the engine is cold. The noise goes away when it heats up and the dealer says it’s “piston slap” and it is normal. What can I do?
Subaru engines have always been pretty loose…I have owned several of them, used them for a Colorado rural mail route. They all clattered a little. Piston slap is pretty harmless and usually will not effect overall engine life. I would use 10/40 oil in the summer and 10/30 in the winter…Maybe even a little “top oil” in the gasoline. 4 ounces of outboard oil per tank of gas will help lube the top end and avoid “dry starts”…Don’t race the engine until it warms up…