Is it true that synth oil is not reccomended in older porsches? The guy at the shop wehre I took my car said this because synth leaks easier (it "finds" leaks or something) and for an older engine it's not as good. Might of said something about the casting technology back then wasn't as good and more likely for little spots the synth might "find" to leak through.... ANybody confirm or deny this? I have castrol 20w50 in there now - is this right?

 

Stories I hear are about the leaking. If the car has not run synthetic all its life, it's a bad idea because it has detergents etc. that can open up leaks. I just put Castrol 10w30 in mine, response on the board was it's okay. 20w50 is pretty heavy for winter in my book, unless you live in the tropics (e.g. Florida). Some people do argue for higher weight oil in higher mileage cars.

B

 

I don't know about how common it is but it did happen to me. I have a 86 944 NA and as soon as I got it, I had the oil changed to synthetic oil. Sure enough, it's now leaking oil. Just a little itty bit, but it didn't leak before I had it changed.

 

It's a tradeoff. If you're going to keep the car, then switch to synthetic and fix the leaks. If you're just going to drive the car around for a few tens of thousands of miles and sell it - then use 20W-50 petroleum-based oil and avoid the leaks.

20W-50 synthetic flows the same at zero degrees F as it does at 70 degrees F. 20W-50 petroleum-based oil doesn't flow quite as well. The old adage that 20W-50 is too thick for winter use doesn't apply to synthetics.

IMHO - 10W-30 doesn't provide sufficient film surface tension in these cars. I wouldn't go with anything less than 15W-40. Remember, it's the TOP number that matters once the engine has warmed up to operating temperature. The bottom viscosity number only applies when the engine is cold.

Greg

 

Greg--

What oil are you running in yours right now? I have noticed that with the 10w30, the oil pressure will be at about 2.5 bar at idle when warm, whereas it was much higher--4-5 bar at idle when warm, with the old oil. Seems the 10w30 at least gives correct pressure, but should I worry about just brute wear? Oil changes are cheap and easy, so let me know if I should change this stuff out right away... Just learning-------

Thanks, B

 

I agree with all of you. I run mobil one 15w40 in all of my cars...and when I change my oil I put the realtively clean used stuff in the van...how is that for recycling?

I have heard and seen the 'new leaks w/ synth' in other cars. I am a firm believer in synth oils and a tight non leaking engine. FIX THE LEAKS.

Enjoy.

 

I agree with fixing the leaks!
Synthetic oils seem to creep out of any gasket that is less than perfect. Also the gasket materials have evolved in more modern cars, so keep that in mind when updating your gaskets.
I prefer semi-synthetic. Full synthetic is very slippery stuff and might cause headaches in a higher mileage motor.

 

what about compromising and going with a blend?

 

I am not an oil expert, but have access to some of those guys through the Valvoline testing lab (no I don't work for them).

Synthetic oil molecules are often smaller than the same weight dino based oil. That in part is how they can be slightly more prone to seepage type leaks. My 944S has used Mobil 1 all its life and is leak free.

Synthetic oil in high mileage engines does tend to cause higher oil consumption simply cause it can slip past the oil ring on the pistons easier. That in part is why no full synthetic motor oil has ever been FAA approved for use in piston engine aircraft. Since Porsches all fly low to the ground (even at Road Atlanta now) We don't have to worry right?

The synthetic blend oils are a great compromise (especially for older engines) as it only takes a very small amount of the synthetic base stock to gain most of the film strenth lubrication and high temp breakdown properties of full synthetic oil.