oil question

[fishtrap3]

Just aquired a 87 s-10 blazer with 190xxx. I am wondering about the benifits of putting in synthetic oil (amsoil). Is there any in a vehicle this old. It doesnt leak any detectable amount of oil. Not sure yet if it is burning any.

I was told that adding syn oil would make it start leaking oil. Something to do with the seals.

[Jeremy airjer W]

One theory has to do with the size of the molecules of oil. Standard oil molecules are not uniform in size so there may be several different sizes. only the smallest of the sizes will make it past the seals

Synthetic oils are by far more uniform in size. If this size happens to be the same size or smaller than the gaps in the seals than yes it will leak more. If it is larger than it will leak less.

There is only one way to find out. Fill it up with sythetic and see what happens. Don't be affraid of switching back to convential oil on the next oil change. This is also a myth.

Personnally I don't think it would be worth it unless it has had sythentic oil for a majority of its life. A guy I worked with had an olds v-8 with a gagillion miles on it. he used conventional oil and was anal about changing it every 2,000 to 2,500 miles. I had the oppertunity to do valve cover gaskets on it a couple years back and there wasn't a spec of sludge or carbon build-up! The inside of the valve covers and the valve train where like brand new. It convinced me that the oil wasn't important, it was the dedication to proper service intervals that made the difference.

[theoilman]

The overall recommendation is "You can use AMSOIL in any sound engine (that is, that it is not leaking nor burning an excessive quantity of oil)."

Specifically, I would recommend NOT changing from petroleum to AMSOIL (or any other synthetic) with 190,xxx miles on a Chevy engine, even if it seems 'tight' now. AMSOIL's better detergent cleaning package will clean the existing gum, varnish, etc. and if that is what is what is holding seals together, it will reveal a problem. NOTE: it won't damage any seals, just the opposite, it will help soften stiff tired seals. But I have seen too many GM engines that it would be a mistake to change from petroleum to synthetic at this kind of mileage.

Of course, if it had been on synthetic through most of its life, stay on it.

[fishtrap3]

Thanks guys.