How would it be to add a cup of kerosene to the crankcase for five minutes or so before each oil change? I flushed my Mazda MPV with a pint of kerosene added to the oil and ran it for four minutes, and it seemed to improve the idle a few months ago. I don't want to over-do it, though, but since it seemed to work I'm wondering about a cup, rather than a pint,added before each oil change.