alanp

When I purchased my '90 C2 the PO had always used 20-50 synthetic motor oil and the car weeped a bit of oil. The last 2 oil changes I switched to Rotella 15-40 dino and ...no leaks. I took it out yesterday for a long spirited run...parked it and put some paper under the motor to check for drips and when I looked this morning....dry..no drips at all.
Any technical reason for this?

Ducks964

If it was my car and there were no drips, I would assume there was no more oil left in it.

sml

Maybe it was wiped during the oil change and one night is not sufficient time for the oil to leak sufficiently to form a drop.

alanp

Last change was 2K miles ago. From what I've heard synth oil has detergents which clean the gunk from gaskets...that gunk created by years of non syth oil builds up and seals inperfections in gasket fit. Returning to dino oil seems to help.

NOTE: this is not verified but just what I heard the other Pcar site....so far tho it has worked for me.

RichiRich

I don't know what my PO had in it, but I was recommended to change it to 10W40 and my leaks stopped too - and it definitely has oil in it

speedbagger

heavier oil, more pressure?

just a guess....

windblown

my p-car shop absolutely told me NOT to use syn oil in my high mile 964 motor. I was told that the thinner syn oil leaks out vs the dino oil. Makes sense if you have ever put your fingers in both syn and dyno and felt the difference.

Streetfighter

I have gone through the same thing when I had my 964. The Rotella is a thicker oil being non synthetic. You have to realize the 3.6 litre was not designed for synthetic oil. When owners have switched to over to synthetic they find the car leaks oil at a higher vs non synthetic. That is due to synthetic being a thinner oil and finding its way through the cracks. Its your car and the decision is yours on what oil you choose to run. A lot of people on here will run Brad Penn which is a semi synthetic that has a concentration of Zinc which is good for the air cooled engine. The owners manual gives you a base line of what oils Porsche recommends for their cars maybe start there or search the archive here to get a feel for different peoples experiences.