Should synthetic oil only be used on new cars or used cars that have used synthetic from start? What about used cars that used regular oil, is it ok to make the switch to synthetic?

 

It doesn't matter.

 

I don't know exactly what the previous owner of my car was running before I got it, but it looked and smelled like crappy dyno juice. I changed over to sythetic at 90xxx miles and did not have a problem. when I pulled the engine apart (heads and cam swap) I was quite happy with how clean everything looked so perhaps it had synthetic run in it at one point in time, then was switched to sludge for a time period. I was the vehicles third owner. obviously if you're engine already has some minor leaks DON'T switch over until you fix the leaks cause synthetic will make those leaks worse by breaking down and grimy buildup that may have partially clogged the existing leak.

 

switched my formula to mobil 1 after i got it with 72k on the clock no troubles now uoto 119k

 

Thanks

 

You will find all sorts of posts and opinions.

 

As far as your question is concerned, you can switch to synthetic even if your car has been using conventional oil all its life.

The question of which is better is always being debated here, and you'll never get a definitive answer.

 

There is a definate answer, but there are still those stuck back in 60's technology (true duals, ripping out EFI to go to carb, etc.).

There are two "issues" with high mileage engines: 1) how much wear has occurred, and 2) how much sludge and varnish has been built up by the use of petroleum oil.

Those were also the issues back when I started using synthetics back in 1983.

#1 is only an issue with oil leakage or consumption. If you don't mind adding another quart every 800 miles at $5 a pop, synthetic is going to reduce further wear. I stick to recommending it for "mechanically sound" engines only.

#2 can be handled in a couple of different way: By a crankcase flush - AMSOIL has had an excellant one available since 1983; or by gradually changing over to synthetic - using one quart of synthetic and the rest petroleum at the first oil change, 2 qts syn the rest syn at the next, and so on until the entire fill is synthetic, changing the filter each time, of course.

Fair warning: A synthetic is not a synthetic is not a synthetic. Stick to the premium offerings (AMSOIL, Mobil 1, Red Line, Royal Purple) and avoid the "me-too" offerings of the others which use an inferior base lubricant that has only been allowed to be called a synthetic by the actions of lawyers and judges.

Since, as stated, this comes up all the time, do a search and sit down for awhile and read, read, read. Just don't believe everything you read ("I used synthetic once and my engine leaked for the first time ever.", etc.).

To preclude more and more of the same, we'll say "Good night, Gracie" to this particular thread.

Oh, about that 60's technology stuff: How many of you are still using bias ply tires? Even drag racing tires are going radial these days.