I'm sure this has come up before, but I'd like to solicit opinions of the good folks here. The Custom Cruiser I was going to go for didn't pan out, the owner decided to keep it, but I'm on the trail of another car (1985 Pontiac Parisienne,) that's reasonably low-mileage and well-kept. I'm wondering if it might be worth it to start running synthetic oil in it. It has about 100,000 miles on it, and with modern conventional oils having become so crummy, and synthetics lubricate better, I'm thinking of it from an engine longevity standpoint. However, I've heard all kinds of things like it could cause leaks, create blow-by and all kinds of other things. Thoughts on how not to confuse fact with fiction? Does anyone have practical experience? Thanks. Charlie Larkin
I never liked synthetics but changed my mind entirely when I tore down an LT1 with 120K miles on it and it looked like factory. No wear and clean as brand new. Never seen anything like it. That engine ran nothing but Mobil One from day one as recommended by Chevy. That's now what I run in rebuilds and built engines. With that said....it is so slick that if you have places that are not sealed perfectly it WILL find them and leak. Same with blow by depending on engine wear. What I do is run it in a car and see if and where it leaks and how it acts. I would have no problem trying it in the car you describe providing those are the facts. It's not a cure for anything in older engines with miles but it can't hurt anything. Try it and make a decision after running what's in there for awhile. Chevy recommends Mobil One right on the oil cap on my LT1.
Synthetics are better in my opinion also, but you may have a problem with the '85 engine gaskets holding the oil in. The older gaskets tend to shrink and dry up, but the conventional oils swell the gaskets up again and seal up eveything. Most synthetics won't swell older gaskets and then the engines leak from everywhere. Also all the new oils have had the zinc and phosphorus content lowered considerably, and that will be a problem with your engine. You may want to think about running diesel oil or better yet a specialty oil that is made for off highway use/older cars, and high mileage oil is not what I mean. Look for an oil that still contains zinc, and phosphorus, and it will say so right on the bottle. Mike
Actually, Mike, that was main motivation for considering the synthetic- the lower zinc/phosphorous amounts. I was thinking that where synthetics simply lubricate better by their nature, that might help offset the missing additives a little. The seals are a question I've had, and these statements seem to be pretty consistent with other people I've talked to. I understand that even the diesel oils will be encountering this issue, too, so I'll start looking for the other stuff. If I can't find that, I can always add a quart of Marvel or LucasOil if I need to. I have considered the semi-synthetics, too, and will look into those in a little more detail, as well. Charlie Larkin
I've used Mobile 1 in all my cars for almost 20 yrs. My first was a bought new 93 full sized Chevy conversion van. 350 motor. I changed over to synthetics at the first oil change. Got rid of the van after almost 200,000 and it still ran like a champ and never burned a drop of oil. Went through 2 transmissions though and was ready for a third. I also go 8-10,000 between changes and have never had an issue. The oil still comes out as clean as regular oil after 5-6,000. My wife's 01 maxima has over a 100,000 on it now and my 05 Pontiac Vibe has 68 + on it. Both bought new and neither has had a bit of a problems. That includes leaks of any sort. The Vettes and all the hypo exotics (Ferrari, etc) require it in their warranties. If your just starting it in a high mileage car I don't know if I'd bother "IF" the car was using oil. Otherwise, go for it! I also agree that the older gaskets may not seal the same with the synthetics.
This is the key point and why, I think, charlie8575 would be wasting his money putting synthetic oil in the 100,000+ Pontiac. I've read that once an engine has been run with non-synthetic oil, the advantage in running the synthetic is lost. You can never fully remove the old oil, so some always mixes with the new, and the advantage in running the synthetic is not as great as it would be if the only oil the engine had seen from day one was synthetic. You're paying a lot of extra money for the synthetic that is not worth it given the only marginal, if any, improvement, that you'll get in engine wear.
One advantage is the oil change interval. Sure you pay twice as much for synthetic, but some brands you can run out to 10,000 miles before shearing. That makes it a savings. Plus, if you don't like changing your oil, that's a good thing too. The other thing is that it clings to metal components, so there is better wear protection during cold start-ups, right when your engine is most vulnerable. Synthetic doesn't cause leaks, but it might make you aware of problems with an already compromised system on a well-worn engine. But 100,000 shouldn't be an issue.
The only issue with longer oil change intervals is that it is a carbureted car which contaminates the oil much quicker than fuel injection. Here is a informative article I found on oil. It will take some time to read. http://www.boss302.com/oil.htm
