I have a fairly old car that has had a lot of stop and go miles. The car is burning oil and the oil gets dark quick. I figure this is due to composits in the engine (sludge). Is there an engine cleaner that will help get the sludge drained out of the engine, or should I use a synthetic, will it help? I take my car to jiffy lube and they have a internal engine cleaning product that they use before draining the oil. Do those products work?