My mechanic suggested switching to synthetic oil to alleviate the puff of smoke from leaking valve guide seals when I first start up my 5.7. He said synthetic doesn't burn like regular oil. Well, now it smokes twice as much! He said it would quit after I drive it more, but am beginning to seriously doubt that. What's the take on this guys?????

 

i have never tried synthetic oil but i do knw of a good seal reconditioner and stop leak that help with that kind of stuff the same thing was happening on my v6 lebaron i a bottle of Bar's Leaks stop leak in it and in about a week it stopped everytime i changed the oil id use that stop leak im a firm believer you can find it most every where including walmart its like 9.99 id try that and id change that oil back to convetional

 

dont even both. synthetic is thinner, thus easier to leak out. notice any oil puddles now under the car? go back to regular oil, and use 10w-40. the car is old enough to use that weight oil, and it wont burn or leak as easily. i was young once (ok, still am) and ran synthetic in my car, much of it had burned or leaked out within 2k miles. i went back to conventional 10w40 and would only lose a quart every 3k

 

Microkid, not sure what you meant by your opening statement "don't even both"?
Anyway, there are no leaks under the car, just the darn smoke on startup; however, have not driven it much since the synthetic oil change. Do you think the 10-40 would change the few drops running past the valve guide seals when it sits a while? There is no smoke if it sits less than a couple hours. Thanks for the reply.
As for the Bars Leak, I sent an email to them and asked their opinion on my situation; will post their reply when I receive it.

 

I agree with the leaks. I just switched over to synthetic on mine and I knew I had a small rear seal leak. About 1/2 quart a month. Now with the synthetic same weight, I leak out about that much every week. Not really worried though as I am doing a cutch upgrade and replacing the rear seal anyways.

 

the bars leaks seals up rear main leaks as well i love the stuff

 

I would find a new mechanic then the one who recommends Synthetic oil for stopping valve seal leaks. SBC engine with hi-mileage are well know to have valve seal leaks and white smoke on the first start up. I had that on my old 305TPI and the only cure is to replace the valve seals.
Never use synthetic oil in older engines unless they were rebuilt.

 

The car only has 29K miles, otherwise he probably wouldn't have recommended the synthetic. The smoke is blue, not white. The guy has always done a good job for me, but I am questioning this move.

 

sorry, i meant dont even bother. my car only had 36k on it when it let go, and only 28k when i bought it. the seals were bad when i got it. usual smoke on start up. i ran the bars no smoke, and it worked for about 1k miles, then started again. it wasnt really worth the cost of the bottle since it burned off. i was still running 5-30 at that time, then switch to 10-40 and it didnt smoke nearly as bad at start up

just think of it as upper cylinder and exhaust lube. now your exhaust system wont rust out!

 

worn valve guides will also help the motor smoke on first startup. it could be the guides were at the large end of the acceptable range when they were done, other than that you shouldnt be seeing any smoke from a 10k motor. maybe a puff, how much smoke we talkin about anyways? is it thick or just adds a bit to the regular burnoff of moisture.