Red97LT1

iTrader: (8)

Hey guys,
I am getting a half dollar size leak under my car now everyday. I still have good pressure and I keep an eye on the oil level. Looks like a rear main seal to me.I also have been told it could be the Lower intake manifold gaskets.I'm going to get under there and clean it up and try to see where the leak is coming from.

I have always use Mobil 1 10w-30 Synthetic but was wondering if I should go to a thicker weight in a regular or stick with the Syn and use a thicker weight.Not sure if it would help at all with the leak or not.Buddy of mine just said that Synthetics tend to leak more if gaskets,seals ,etc are bad.

nascarnate326

iTrader: (1)

I switched form M1 to regular oil to "fix" a leak I have, it made it much worse.

You will just have to try and see what happens.

Red97LT1

iTrader: (8)

Thanks for the info. I'm going to use some M1 5W-30 and see what happens.

jaxcam02

iTrader: (1)

What I have heard is that a synthetic oil will swell the size of the gaskets due to the detergents and help "hydrate" the gaskets. Once you go synthetic you dont want to go back to conventional or semi synthetics because your gaskets will shrink and crack thus endusing a leak or making any leak worse. I switched from synthetic to conventional on my old 3.8l and it just made the leaks worse. If I am wrong someone correct me but from what I have read and heard you never want to go back and fourth.

LS1121

iTrader: (17)

The POS PCV we have on our cars rots away and can cause what looks like an oil leak. Check the rear of the driver side valve cover for oil and check the valve cover also. That is what caused me to FIX my PCV system.

Crimsonnaire

iTrader: (1)

Also don't forget the oil pan gasket. A leak from this gasket will yield an identical appearance to that of a rear main seal leak. If you can't isolate it from the outside, take it to a shop that offers free initial inspections and have them remove the starter to see if there's oil spewed around the inner surface of the transmission housing. If so, it's the rear main.

Synthetic oil is more slick, thus creeping through crevices quicker. If your leak is already at that severity, you most probably won't reap any benefits from the additives in the synthetic oil. The leak may only worsen. At such a point, the only effective thing is either replacing the faulty part or stop leak addtives which you do not want if you intend to give the engine longevity.

LSPoncho

Before I swapped in the LS, my LT did the same thing. My leak was from the rear valley seal on the intake manifold. Apparently, GM did not put high temp sealer there and the heat from the EGR line melts the sealer. I would avoid trying to "fix" oil leaks with different viscosity oils or types of oil. Any change in the leak would be temporary or coincidence.

xhifer

I used valvoline max life 10w30 and it helped minimized my leak significantly on my old 190k z28.