Mine does that once in a blue moon, but I have 187k on it. For the last several years I have been running rotella in it just recently I went with the 10/30 rottela and it seems to like it. I would try the rotella with maybe a quart of mm oil in the crankcase and a heavy dose in the fuel and take it for a blast. Btw mine uses no oil between the 5k oil changes so maybe the rings never seated or one is stuck???