hi

synthetics dont cause leaks, but the esters they contain do such a good job at cleaning the residue that dino has left behind ( which actually may be acting as a type of bandaid on these worn seals) that these seals begin to leak.

the esters didnt cause the leak, they just removed the residue which was holding it nall together.

if you have a leak, or have used dino , try using auto-rx before changing over to a synthetic.

That'* partly correct.
The seals on newer cars are a different material than the older car types and the tolerances are a lot tighter also.
For instance Viton rubber stands up to the synthetic "esters" the best.
Viscosity of the oil has a lot to do with it too.
My Firebird rear main seal leaks like a sieve if I use Mobil 1 10W-30 but hardly at all now that I've switched to a heavier weight 5W-50 Synthetic.

What is the prefer type of synthetic oil for GM cars?

hi

"partly correct" .. ?

it is correct. your rear main leaks because the esters have cleaned the dino debris from the surfaces and revealed a worn seal.

the thicker 50wt will mask the damaged seal much like the dino probably did previously with its deposits.

if it was me, i'd replace the rear main, and use the M1 10w-30.

my cars never leak. i do a initial treatment of auto-rx with dino penz 10w-30, and then go to the M1. with cars over 100k, there is slightly longer treatment plan, but again..no leaks.

for the record, you should be fine with 10w-30 M1. I prefer that over the 5w-30 as its TBN seems more stable over the duration of the extended drain interval.

114k i switched, just drained the dino, and put in syn. No leaks!! But then again, my engine has been pampered

Very interesting guys. Over my head, but still interesting.

I ordered my free kit. With a new engine I want to keep tabs on it from the get go. But how often should you run the analasys to get an acurate reading? Every oil change, every other etc. :?:

hi

if this report comes back favorable, and both you and the lab likes what it sees, i'd stick with the oil and the change interval.

depending on how and how much you drive, i'd probably do another in 3-4 changes. but if you change anything, you might want to "lab" the oil, just to see if these changes are positive or not.

Thanks, that is awesome. I never knew that oil analasys was possible or even probable. That is not only interesting, it can possibly save your engine and alot of money. Again thanx!