billthe3

I had the car at the shop today getting an oil change and the tires balanced and whatnot, but when I was doing the stuff as I dropped the car off the guy asked if I used synthetic or non-synthetic oil in the car. Upon asking why it matters he said that you can't switch between the two, or aren't supposed to.

There any reasoning/truth to this? Seeing as there was no sythetic when these cars were new, is everyone that is running synthetic running a rebuilt motor?


They also found out my rear sway bar didn't have any bushings on it...

KLR

Do a search on this and you'll find more than you ever wanted to know. In short, there is no harm to switching from regular to synthetic, but you are likely to develop oil leaks due to the detergents cleaning out some gunk and/or the smaller molecules sneaking through in places where non-synthetic can't. If you're car is doing fine as is, I wouldn't switch. The theoretical payoff for a street driven car does not outweigh the potential cost of having to do a cam tower gasket, oil pan gasket, etc. sooner than you otherwise would have. Even minor leaks in a 951 can be a real nuisance as they are likely to land on the crossover or some other exhaust plumbing and smoke. It's no fun having pedestrians look at you funny for this. Don't ask me how I know.

GodSpeed

i have ran mobile 1 synthetic for years and recently switched to royal purple. never had a problem and no leaks.

SwiftyZenBadd

dan
ive been thinkin of going to royal purple, 15w40 what weight do you use?

ehall

I use AGIP 10w-60. Love it.

billthe3

Ok, thanks for all the advice. This was the first oil change I've gotten done on the car (and it was marvelously late in getting it too!), so I just wasn't sure what to say. Ended up just having them do non-synthetic.

Trucho-951

I think running synthetic is an overkill. I was running Mobil-1 15w-50 and got tired of paying so much for 6 qts. every oil change. At the advice of other rennlisters, I've switched over to non-synthetic Valvoline Racing VR-1 20w-50. The car loves it, and most importantly, my wallet loves it.

Serge944

Synthetic is indoubtably better (especially for your turbo), but I wouldn't switch to it if conventional oil has been working well, maintaining adequate oil pressure, and not leaking.

I use 20-50 VR1 too. My friend uses it in his 911 race car as well (mixed in with some straight 60 for thickness). It's good oil and almost half the price of M1.

sharky47

I am currently using Mobil-1 synth 15-50 in two of my cars.

billthe3

Has anybody personally seen/had any issues with switching over to syn from non-syn and getting leaks or whatever?

Serge944

Yes - I burn and leak more oil with synthetic. It got completely out of hand with my previous 944 and its tired seals. Problem is, if you decided to switch back to conventional oil, the rate at which your engine leaks might not return to how it was before switching to synth.

If you want to give it a try, go for a synthetic blend first.

KLR

Yep. I switched because I thought my car, with mostly new seals, would be unlikely to leak. Wrong. The cam tower gasket had never been done and almost immediately started to seep near number 4 -- right onto the crossover. Smoked like mad. I'm sure that this would have eventually happened with dino, but it was no fun paying $700 to replace that gasket 6 months after having done a timing belt.

Reflecting back on that experience, I'm not even sure what I was trying to accomplish. My car has done another 20k since then, the original turbo is still doing fine, and my oil pressure remains perfect on my original rod bearings. This is at 131k. How much better will my car do on synthetic?