pcarfan944

I recently read (sorry if it was here and this post is redundant) that once you use synthetic oil in your car it's bad for the engine (seals?) to use normal oil once again. Can someone shed some light on whether this is fact or fallacy?

Pat
86 944

Strike-Force

well i ran 15w-50 mobil 1 full synth in my car for years. then i stopped noticing the difference, and now i run castrol gtx 10W-40 normal and I can't tell a difference. just make sure you let the oil drain real well in between changing from synth back.

Chris_924s

The question is- does synth cause leaks? I think no. It propagates through existing voids due to it's higher (and longer term stability towards) viscosity.

Dino oil will thicken and plug small voids.

YMMV- this is only my opinion from my experience.

Zero10

Sorry, but why would you switch back?... I would never run anything but synthetic (in specific, Mobil 1, or Amsoil) in my 944, and I can't understand why other people wouldn't.

But no, it will not make your seals incompatible with conventional oils, don't worry =)

pcarfan944

[QUOTE=Zero10]Sorry, but why would you switch back?... I would never run anything but synthetic (in specific, Mobil 1, or Amsoil) in my 944, and I can't understand why other people wouldn't.
QUOTE]

Besides extending your oil change intervals by a few thousand miles, what are the other perks of using synthetic oil? ?

Dave951M

I run nothing but 20W50 Valvoline Racing in my 951, it already has leaks, and changing to synthetic would only drip more. The key is to make sure you have regular oil changes, more often if you flog it on the track.

KuHL 951

The main reason for me is the extended change interval (5K), cold start superiority, and the fact that "coking" at the turbo is 'reported' to be significantly reduced or completely eliminated. If your car leaks then fix the leak. Mobil 1 does seem to find the exits easier. For the price of an oil change I've always felt it's worth the x-tra Porsche dollars.

Dave951M

Yup my car leaks, but the price of fixing it means removing the oil pan. I can add a quart or two every couple weeks to live with it for a very long time. When it gets to the point of an oil slick on the garage floor, then I'll go ahead, jack it up and fix the oil pan gasket. I tried switching to syn, and prior to that, I had no leaks. I did after switching and going back has only made the leak much smaller. No, the switch didn't cause the leak, 180k+ miles probably has much more to do with that. That said, I still maintain it's best to change your oil on the recommended intervals, and sooner if you track the beast.

seb928s

I don't know where you people find this stuff. Will it cause a leak or is it bad to change back to dino. Syntectic oils are much more better then dino and switching to one or other doesn't harm anything. I use the 3k oil interval for the synthetic oil. There is a differance between how much protection you get from dino to synthetic and it's worth the buck.

Strike-Force

i think i changed mostly the same reason as dave951M. i have a small leak and i put a quart in every roughly 500 miles. it would be too expensive and not cost efficient to run synth anymore.

Dave951M

Seb- how many race cars have you worked on or maintained?

seb928s

I worked on one track car but many other street cars. Why?

Dave951M

Thought so. I ask the question as your response would lead me to believe you don't have much time in either engine building or track/race car maintenance.

With your comments on syn being sooo much better than dino, I seriously beg to differ for the average street car. If you do the normal change interval, use a good quality oil and aren't thrashing the car, there is no real advantage to syn over dino for an old 944 other than weight reduction, mainly in your wallet. IF you are seriously tracking the car on a regular basis, then a case can be made for syn. If you insist on putting it in the daily driver, go ahead, it's your comfort level. As far as dino goes, Valvoline and Castrol are the best I've seen. Quakker State is the worst due to high sulphur content leading to "gunking" in the crankcase. In case you've never had to deal with it, it looks like and feels like, an oily Jello. Newer cars that started out on syn, I'd stick with syn, but topping off with a quart of dino when needed won't hurt it. Still, I'm sticking with dino for my 180k mile 951 until I get around to rebuilding the engine and turbo which I hope is another 180k miles in the future. It still leaks the same amount as when I tried the switch a couple years back and consumption is the same as well.

hosrom_951

Just make sure that your car was not running on normal oil for 60K+miles then converting to synthetic.

It's alright vice versa (from synthetic to normal).

seb928s

Yes but my car doesn't leak the oil which I see your point if for using dino in your street car. I know Quakker state is bad so is pennzoil. I work at an oil change place. We mostly sell castrol oils as we are a dealer for them. Syn oils do help with running hotter that they don't brake down as much. I rather spend the few bucks more and run synthetic oils. Mostly people just use it for the longer interval for synthetic oils and it does come out looking better when even overdue then dino oils.