From what little I know, based on your description, I would not flush those engines! Doesn't sound like they need it at all.

crzydmnd72, I think I remember a post about that too, I think thats what I am going to do. The natural route sounds the best to me

I have used Marvel Mystery Oil and this seems to do a great job. It is not as drastic as a flush, you put it in with fresh oil and leave it in until next oil change.You will see the oil get dark soon if you have alot of dirt or if your engine is clean it will not change color. It is not a new item and has been proven to work well. It can also go in the fuel tank to clean carbs or injectors and in diesel fuel. Instructions are on the bottle and its not expensive

My 88 will turn 229,000 (miles) probably by the end of the week. Gunk has been used virtually every time the oils been changed since my family got the car back in the early 1990s. Im confident in saying it'* a good product to use on our engines. Just my .02