Rep Power: 910

oil is apparently coming from the lifter valley, seaping through the head gasket and out the back of the head. i dont feel like spending $150 in parts and a whole sunday tearing my engine apart. i put some stop leak additive crap in it that i was told was the best, so far its been 3 driving hours, the bottle calls for 5 to take effect.

well i remember hearing that if you use conventional motor oil and have small leaks, and switch to synthetic, the leaks may worsen. well would this work the other way around? if i switched from synthetic back to conventional would there be a chance the leak might stop for now?

 
Rep Power: 727

Yes. Its a possibility, depending on the size of the leak. I dont care what people say about Synthetic vs conventional and the weight ratio being the same, conventional is thicker.

Regardless, it'll be a hell of a lot cheaper doing a simple oil change than trying to fix it heh.

 
Rep Power: 866

i will never use synthetic oil in an LT1. LT1s always leak, and Synthetic leaks more than convetional. im stickin with my 10-40 valvoline.

 
Rep Power: 729

I use synthetic in my LS1...No leaks 4 m3

 
Rep Power: 702

5w30 synthetic in my old school 350 and my '04 3400.

 
Rep Power: 1069

hate your engine that much (every manufacturer says NEVER EVER use 10 w 40 it is bad for the engine) I have yet to see a licensed mechanic who has found leaks caused by synthetic oil it doesn't happen, they are required by regulation to have the same viscocity (that's teh flow rate or thickness)

 
Rep Power: 727

Now you have. lol

 
Rep Power: 0

synthetic here no probs

 
Rep Power: 759

I switched from Mobile 1 synthetic to Valvoline Max Life 10w-30 due to a small leak. I noticed a major change. The leak is almost non-existant now.

 
Rep Power: 727

#2. lol

Im tellin ya, Synthetic is the devil for old engines imo. If I had a brand new engine and wanted to spend the money (yes I know, synthetic lasts longer, so your not spending that much more) I might get it. But, I guess I like going with the tried and true method of doing things rather than changing them and causing problems.

 
Rep Power: 866

how can an engine oil be bad for an engine...

 
Rep Power: 1069

the weight is too much for the pump to pump well, it's too heavy to cling to bearing surfaces, the film thickness is off meaning your bearings have either too big or too little a gap

 
Rep Power: 1069

max life has additives to make your gaskets swell to stop leaks (it says it on the bottle)

 
Rep Power: 1069

so your an ASE certified mechanic who has done major rebuilds?
as for teh flow differences check ou theis chart http://www.bobistheoilguy.com/visc.html
synthetic oils

Oils produced by synthesis (chemical reaction) rather than by extraction or refinement.
Many (but not all) synthetic oils offer immense advantages in terms of high temperature stability and low temperature fluidity, but are more costly than mineral oils.
Major advantage of all synthetic oils their chemical unformity.

 
Rep Power: 727

Yes I am Arch. But 99% of the people in the automotive technician industry are 'ASE' certified, because there are so many fields. No, im not an oil guru. But I am an 'ASE Certified Technician'. I am just telling you from my own experience.