I know that this topic has been beat to death on this forum but I had a little different question.
I just bought my 02 Z28 M6 a month ago and right when I got it I did an oil change. After the oil change I noticed my rear main seal has been leaking about a inch wide spot, so I have been watching it and only had to add a small amount before my next oil change.
When I did the the first oil change I used Mobile One Synthetic 5w-20
after doing some more research ive be seeing that 5w30 is recommended.
By changing back to the right weight, will I possibly stop this leak or at lest slow it down? Or am I just screwed? I dont mind dropping the tranny and changing the seal as I want to do a new clutch anyway, but not for at least 6 months or when money isnt so tight. If this would fix the leak that would be awesome, any input is welcomed. This just goes to show I had the resources and didnt use them, guess I learned my lesson.
Your welcome to flame me for doing this but please leave your opinion on my situation too haha

 

If youre capable of drooping the trans replace the seal but dont be like me and do it twice cause you didnt think to replace the rear cover gasket while all that crap was out of the way

 

I doubt a different weight would cause a leak, plus 5w-20 compared to 5w-30 is such a small difference it wouldn't make a difference in leak prevention. Drop the trans and replace the rear main seal and then and the rear cover gasket while you are there.

 

I guess I was just hoping for a miracle on this one, but oh well. I havent pulled the tranny on an ls1 so far but I have a couple of buddies that can help and get it done. If im not mistaken I believe the oil pan could be due for a new gasket. and its a pretty tight fit. Can it be done without taking the motor mounts loose or should I just stop trying to take the easy way out on this one?

 

The cheapest and quickest way to see if going back to the 5w-30 will stop the leak is to...change back.

If that doens't work, proceed as you wish. But for $26, what's the harm.

 

No point in changing the rear main for a 1" drop of oil.