Synthetic in a leaky engine?

Messages
233
Location
Pullman WA
My question is that if you have a car that already leaks oil (less than a quart between oil changes) would switching to a synthetic really cause it to leak more oil than it is presently? It's a 1992 Buick V6, and I'd like to try a synthetic in it. I can't see how switching to synthetic would cause it to leak even more oil. Comments?
 

Patman

Staff member
Messages
21,989
Location
Oakville, Ontario
A lot of synthetics are thinner at operating temp than dino oils of the same viscosity, so this can cause leaks to get worse right there. Another thing is that PAO based synthetics have a slight tendancy to shrink the seals too, which can exagerate an existing leak. Most good synthetics will blend their base oil with both PAO and some esters though, since the esters counter the PAOs by slightly swelling the seals. [ November 29, 2002, 02:30 PM: Message edited by: Patman ]
 
Messages
534
Location
South
I have been told by Mobil Techs that synthetics can leak due to the fact that on an older motor the dino oil never reached certain gasket areas so they dry out. Introduce a synthetic and it will hit these locations and come right through.
 
Messages
690
Location
Fort Smith, AR
Okay, so once the engine starts leaking from a using synthetic, how do you stop the leak? Go back to dino? It took my 95 E150 just 3K miles on synthetic to start leaking like a it has a hole in it somewhere.
 
Messages
5,785
Location
Dixie
Roger, I'd change back to a petroleum oil and add a bottle of "AutoRX". Run this combination for 500-750 miles and see if the leak will stop. If it does, you can follow their recommended procedures and probably go back to the synthetic without the leakage .... I've been using this stuff and it really does stop certain kinds of main seal leaks ....
 
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