I'm about to switch over to synthetic oil, but I have heard that it seems to make oil leaks (from seals mostly) worse. I have small leak from main seal, and it would be more trouble to replace than its causing.

Question- Is it OK to use "Engine oil Stop Leak" or similar product to slow leaks from dryed seals while using Synthetic Oil?
I would assume that it is OK, but the cans/bottles of "Stop leak" dont specify. Just thought I'd check since I can. :-D

Synthetics cause leaks, is just more old mechanic bullshit.
No it is not OK to use stop leak type products.
Do not use oil addatives. They don't work. Oils are formulated to work by scientists. Most addatives are formulated by morons that think they can achive something scientists did, or didn't do for reasons in the first place. They all fail at it. Bobistheoilguy.com



You need to fix the oil leak. Buy a bottle of RTV Ultra Black. Wipe all around the main seal area, then clean it with rubbing alcohol. Acetone degreases even better, but don't stay around it, or use too much.

Build up a big ridge of Ultra black RTV all around the area it's leaking & don't touch anything for 24 hours.


The leak will slow, or stop, but it will still not be fixed.




Flush the crankcase oil first. Buy & use Seafoam, Marvel Mystery Oil. You can also add a quart of Kerosene/Diesel fuel ontop of your old oil & let an engine idle for 10 min. It is dangerous to let them idle more than 20min. It's not just the thin fluid you put into it, no car/engine maker suggests letting a car idle over 20min in the first place.

Any of that will clean the sludge & gum out fairly effectively.


Less you buy a super specialty oil, use Mobil 1 Synthetic. It comes in big jugs @ Wall-mart for normally around $18 & is the best oil you can easily buy anywhere.




I suggest directing oil related questions to an oil industry forum.

Bobistheoilguy.com is very popular & has people that actually know a ton about the subject.

I'm about to switch over to synthetic oil, but I have heard that it seems to make oil leaks (from seals mostly) worse. I have small leak from main seal, and it would be more trouble to replace than its causing.

Question- Is it OK to use "Engine oil Stop Leak" or similar product to slow leaks from dryed seals while using Synthetic Oil?
I would assume that it is OK, but the cans/bottles of "Stop leak" dont specify. Just thought I'd check since I can. :-D


I think the myth that synth oils cause oil leaks may be due to the fact that synth oils don't have as many aromatic(spelling) properties as dino oil. This property tends to slightly swell oil seals. So when you switch you may see some oil leakage. I swapped my 94 over and had no problems. If you have a front end leak it could be from the oil pump shaft, camshaft or front crank seal. When they leak it all kind of looks the same as it comes out of the timing belt cover and gets all over the place. If one is leaking they are all about to so it makes no sense not to replace all three. Those can all be replaced the next time you replace your timing belt. Hint, loosen the oil pump drive sproket bolt b4 you take the old timing belt off. Other wise it will be more difficult to loosen it if you have to hold the tiny sproket installed. Access to the crank and oil pump are thru the r/h wheel well, while the cam is from on top after you slightly loosen the first bearing journal. I usually take a good sharp awl and punch a hole in the seal and then pry it out. You must be careful not to touch the crank, cam or oil pump shaft with the awl. Just tap the new seals in place. Be sure to use the right torque spec for the cam bearing journal. Good luck, Steve