A good friend of mine is 50 and has a 97 Z28 M6 with about 50,000 miles.

She's owned it since new and never abused it, it's totally stock down to the skip shift and is probibly one of the nicest LT1's around. She's a total maintance freek and doesnt skip on anything.

The car was a weekend toy up untill the last year, now it's a DD for her husband (also drives lightly on it) and she said that now that it's getting older she tried Mobile 1 and that the performance went way down and it actually started to leak some on the garage floor.

She got it changed back to a regular grade oil and said the performance returned and it no longer leaks.

My only thought is that with the miles and switching to a synthetic so late in age that the oil slipped through the gaskets and jokingly said to her that "your car must be too accustomed to running on mud"

It's truely a beautiful car for a 97, and drives like new, I've always used Mobile 1 in my Camaro since new and havent had a problem (or noticed a performance improvement) but continue for some reason.

What do you guys think? I'm just curious

~Chris

 

If the engine has only used dino oils, sometimes when switching to synthetic, can cause a leak..... Conduct a search on synthetic and you will see a few threads on this subject...

 

It's ashamed but a good synthetic oil will normally cause oil leaks in older cars because the molecules are smaller and that causes leaks easier. It won't however cause a negative change in performance. Can't figure out that one.

 

If synthetic makes leaks more aparent, would going back correct the problem?

 

If more oil is getting by the rings and/or stem seals, then there's your performace loss. Doesn't have to be real noticable to kill power either..

Dave C.

 

Bingo!

It'll kill your oxygen sensors and Cat too. It takes as little as one tablespoon, or so I've heard.


As has been mentioned before, often by me; synthetics WILL uncover leaks that Dino had plugged.

If switching to synthetic made the engine run bad, suggesting that oil was getting past the valve stem seals and/or ring; then it's time for a rebuild on that motor. It wouldn't have to be a total performance rebuild...

As long as you don't have a big ridge, just run a bottle brush honer through the block, do a ring & bearing kit, and freshen up the heads, to include a new 3-angle valve job.

JUST that will add a noticable amount of power.

 

I am having my heads cleaned and reworked before I put them back on my motor. Should I worry about oil leaking somewhere in the block, or are the heads the most likely problem source?

 

I sitched to mobil 1 synthetic at 120K and have had no leaks and car runs great....