WillDC7

Nobody around here seems to like synthetic oil very much, but I've noticed that just about everyone who's tried it loves it, and that most engine builders recommend it. Are there any possible negative consequences of switching to synthetic with 102k miles already on my engine?

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86 Trans Am WS6: The muscle car lives

Vader

Will,

The only possible negative effect of using fully synthetic oil on a high-mileage engine is the potential for increased leakage. If your engine has any oil leaks now, they'll only get worse with synthetic.

This problem has nothing to do with the oil attacking the sealing materials, but its tendency to clean sludge and varnish from the engine. If you already have a leak, some of the leak is probably "sealed" with oil varnish and gum deposits. The synthetic will clean these deposits away and turn your small leaks into full-fledged drops. If you have no oil leaks, you should have no problems.

Since the synthetic will clean your engine inside as well, you'll have to be strict about your oil change schedule. Much of the sludge loosened by the oil will be trapped in the filter. You may want to change your oil filter a couple thousand miles after changing the oil, then top off the oil to the proper level. After that, get on a regular schedule of oil changes. I still like to do mine at 3,000 miles, even on synthetic. As long as you don't "cheat", you should be able to get 6,000 miles on a change. I'm just a little ****-retentive about my cars.

Later,
Vader

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"Some Body...Someone"

tuc007

go for it, synthetic is the way to go, but like vader said, if u have oil leaks, the detergents will trigger them, ive used valvoline synpower but most of the boys here prefer mobil 1

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Morgan

Synthetic oil is a really clean oil with some detergent additives like whats in youre ATF, it alows your engine to spin more freely so to speak, I dont use it cause of the price, I do have some customers that swear by it, but there is always the potential for leaks in older cars.

bubbz89rs

i have used mobil 1 5w-30 for over 140,000 thousand miles now and i have never heard a tick,knock,ping,etc..

a buddy of mines dad used mobil 1 in an old pontiac station wagon and it NEVER had any internal problems when he sold it with 500,000 miles on it. mobil has been around for 130 years and i would never use anything else, i dont care if cost me $30 in oil everytime i change it, i swear by MOBIL 1

FastBroker

Mobil1 is good stuff. Pulled my heads a while back to do valve seals/guides/pain them and the cylinders had all the cross hatch honing marks on them... 70,000 miles, too! not too shabby. Really does clean the engine, too. Also, has much higher vapor temp so PCV will run cleaner... I go 6-8k between changes but miles are not too hard... Put synthetic in trans, too. Good stuff!