Does oil viscosity have anything to do with RMS leak?

First I would not think oil viscosity would have anything to do with a RMS leak... but recently after switching to Mobil 0-40 from 15w50 it is leaking! Is this just coincidence, or does my 996's previous owner knows a trick to prevent a leaking RMS?

This is debatable, but I, for once, believe it encourages seal leaks. I also do not believe you should be running 0W40, regardless, in your neck of the woods. Run 15W50 all year.

0w40 was recommended by several CA dealer mechanics. The engine revs a lot happier with the 0w40 and the gas mileage went up also.

First I would not think oil viscosity would have anything to do with a RMS leak... but recently after switching to Mobil 0-40 from 15w50 it is leaking! You are right, one has nothing to do with the other. You can however sometimes mask an oil leak by going with an oil which has a higher viscosity. You probably have a very tiny leak which is "cured" by the 15W50 oil.

It is true that, when cold, your engine will have to work less when you use the 0W40 oil compaired to 15W50. However, once you reach operating temperature, there is no difference in performance, but there IS a difference in the level of protection. All materials contract and expand as a result of temperature, including crank, block and seal. If at the time these changes in size, there is water (0W40) being splashed about, there is an increased chance that some of this oil will find it's way between the seal and engine. As this process continues, the seal will begin seperating from the crank and block. This seperation will be immeasurable, but the thin oil barrier that now is between the seal and block and or crank will not hold the extreme pressure created by the engine at high rpms. This will encourage oil, high crankcase pressure is present, to begin seaping past the seal, more and more until a permanent, non presurised leak developes. For this reason, not only do you need to engure that engine pressure is minized until full warmup, but you need to you an oil somewhat thicker than water.

The internal oil passages were sized for the flow characteristics of 0W-40 synthetic oil. While it doesn't get cold enough in Chino Hills, if you were to drive up to Yosemite or Reno to go skiing and leave the car out overnight in subzero temperatures you and the engine would definitely know the difference in the morning. Porsche determined that a number of engine failures were due to inadequate lubrication in cold conditions. Because of the high viscosity of 15W-50 in cold conditions there was inadequate oil flow resulting in bearing failure. There is a reason why Porsche recommends 0W-40, and a very good one.

The oil passages were sized for 0W40 oil? I thought I heard it all. I guess the oil passeges in my car (which was factory filled with 15W50) must have shrunk so it only can fit 0W40 now? Remember, Porsche DOES NOT recommend 0W40 oil, but only includes it on the "approved list". And this list has changed half a dozen time or more over the past few years. The egines have not changed. The oil has not changed. Just their approved list has changed. So, did Porsche make a mistake when they approved and filled the earlier 996's with 15W50 or are they making a mistake now. I know that many think Porsche knows all things, but it is very clear that, in the case of the oil they use in these cars, that they have made a mistake. You just need to deside when that mistake was made.

Here's my take: I change my oil/filter at every 5000 mile intervals, Some may say that is too soon but it's what I do. Twice I used 15/40 and the leak persisted. So I went back to 0/40. My 7th RMS suddenly stopped leaking about 6000 miles back and has not leaked since. I did an oil change about 1000 miles back and still no sign of any oil leak. The 7th RMS did however leak for several thousand miles after fitted. It just stopped all on its own. The only thing that has changed is that I changed job back in August last year. The new job requires that I commute to Cambridge from Liverpool each week (about 220 mileas each way). The oil leak stopped around August/September. It may be just a coincidence but I think the reason it stopped is that I now use the car more. I do a minumum of 500 miles each week and its at motoroway speeds. So maybe the answer is that parking the car up after short jeourneys is the cause. I dunno. Anyway, it would seem, I am RMS trouble free at last!!!

This was almost identical to what the Porsche dealer mechanic had told me about using 0w40s. He also told me that all the dealers are now using the 0w40 fill for the 996s, but the 993s are still using 15w50. FWIW, I drive my 996 about 4 times a week, 30 minutes of highway driving each way. No RMS leaking problem prior, the RMS started to leak after a 4 hour business trip one day.

Honestly, I think it is one big crap shoot with regards to RMS. I have just about 60K now on my engine and it has been the best car I have ever owned. Not a leak EVER! Oops, I forgot, it did lead once, but that was the &#%$^&*@*! coolant tank I do 0w-40 in the winter months (Oct-Mar) and 15W-50 in the summer months (Apr-Sep). I do most of my tracking from Mar-Oct.

Haven't seen your posts in a while Bernie, good to see you still around...

If you want something a little thicker than 0W40 but not too far off what Porsche recommends... go with 5W40 from Amsoil or LiquiMoly... they are better than Mobil 1 in terms of qualities such as antifrothing and burn less than Mobil 1 as well... the added weight won't hurt a bit since it is so close to 0W40... for me here in Canada... especially in the winters... the 15W50 is just too thick for winter startups.... or find a good 5W50 as a happy medium and see how it works out for you...

Cheers Torags, been lying low in my new job. But still here on the side

Is 5w 50 anygood? Thats all there is in Australia at the moment (well at least at Super Cheap Auto and Pep's -large auto outlets in Australia)

This topic was discussed quite a bit over at Renntech. A good compromise for those of us living in northern climates seems to be Castrol's 5W50. However, if I lived south of the Mason-Dixon, I would run 15W50 all year long. As is, in NYC, I just had my car refilled with 15W50 this time round (with the dealer's blessing), though I keep it in a heated garage. If it were to ever spend any significant amount of time outside in Vermont (where I ski), then I surely would run the 5W50 all year.

Is there even a fully synthetic 5W-50 on the market?

Here's my take: -My car is MY 02. At that time 0W-40 didn't exist. The owner's manual recommend 10W-40. So I try my best to put in 10W-40. -I know that Joel Reiser of PCA Tech Guru preaches on the 0W-40 for it's thin characteristics to immediately power the hyd lifters. **My take is to keep using what the car was intialy/engineered for and as the the owner's manual specifies. Which on my model year and older 996 is 10W-40 . Track 15W-50. I believe that too thin of an oil has more capillary characteristics or has a high potential that it will seep through vs thicker oil. Like the lister above mentioned "Porsche DOES NOT recommend 0W40 oil, but only includes it on the approved list" for model year 02 and older owner's manual, pg 170 states that: Use only engine oils labelled as API SH or SJ, or ILSAC GF 1 and viscosity grades of SAE 10W-40 or higher.

Mike, I would have to disagree with your logic. Think about your car as a human body that needs "X" to run optimally. With time comes advances in the "X" your needed for optimal performance. When that new technology is available it is wiser to move towards it since it has been shown to be more effective. There is NO reason to run 10W-40. You are selling yourself short on the low temp side but still equal on the high time side. Better protection and lube down in the lower temp range. Like I said, I do 0W-40 and 15W-50 depending on tiem of year.

Dell, the the best of my knowledge, Castrol's Syntec 5W50 IS a fully synthetic motor oil. Since you guys tend to know more than me, I included the link to the spec sheet so you could check it out to know for sure. http://www.castrol.com/liveassets/bp...syntec_usa.pdf

I have two bottles in my hot little hands Dell! (Mobil 1)

Mobil 1 5W-50???

My two cents worth... Experience in other older non-996 engines with some miles on them, all kinds, Porsche, Mopar, etc. shows me that switching from non-synthetic oil to Mobil 1 DOES OFTEN causes some leaking. Somehow the synthetic fits through smaller gaps easier, making gaskets and seals leak. I know this used to be a big debate, but AFAIC it's fact. So, it would seem that a thinner grade of Mobil 1 would leak even more. My 996 doesn't leak enough to form any droplets, but the bellhousing area isn't dry as a bone either. Running 0W-40, but considering switching. Don't know if it's ever had the RMS replaced as I got it used from a stealership with no service history. Another question, why are people so concerned about the tiniest amount of seepage from these seals? Lots of cars do that. (Older American iron V-8's managed with a hunk of cotton rope for a seal and didn't leak. :-) ) Bill

Yes Syntec 5W-50 is fully synthetic. I use Mobil 1 10W-40 which they make in Extended Performance line. http://www.mobil1.com/USA-English/Mo...ce_10W-40.aspx

10W-40? You are really sacrificing protection at the lower temps in the winter during start-up. Do you run the 0W in the winter?

Dell, Point taken. Thanks, but It seldom get below 0C/32F here anyway in Chesapeake VA. Like I said for model year 02 and older owner's manual, pg 170 states that: Use only engine oils labelled as API SH or SJ, or ILSAC GF 1 and viscosity grades of SAE 10W-40 or higher . If you look at the specs of 0W-40 too, it only has the "API SM/CF". Not the API SH or SJ, or ILSAC GF 1 that is written in the manual.

I just go back to the whole "advancement in technology" argument. Either way, I honestly think it comes down to how you drive and take care of your (not specifically you) car regardless of your oil choice unless of course you are in the heat of the south/southwest during the summer (then go with the 50) or in the firgid north (then go with 0W). But for everybody in the middle, I think all these weights are fine.

Hey Dell, This is whats good about rennlist. We discuss for the betterment of our understanding. Dude I agree with you on the cold start up and the 'advancement in technology' theory. No need to convince me any further. Specially if I live in Canada or North East States. But like you said, here in the middle, where I live, I favor the consistency of the shallower grade oil (like the 10W~40 than the wider 0W-40) that it provides during my high rpm runs. I put more importance to that. Somehow the engine sounds looser(more clanking) with the 0W-40 than when I have the thicker oil in it. I know that it take just a little bit more effort to push the thicker oil, but I favor the better protection(I think) it provides.

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Actually Syntec is not synthetic. It is made from dino oil stock with some molecule ************. It does however past the US definition for synthetic - but not the European definition. Now Mobil makes the same compound & sells it as syn in the US, they increased the price of their old syn, now call it European or super syn. big lawsuit tween mobil & castrol

5w 50

Yes, I also have three liters of IT waiting in my garage. Thorsten

What about Castrol RS 10W60?

Torags, That was 2 years ago. Castrol lost the suit and they finaly revised their fomulation.

Thorsten, how did you manage to get your hands on that? I have NEVER seen that stateside. Any good sources to order from with 'reasonable' pricing?

Follow his link. It is from the German site.

Can't purchase though....or rather, it doesn't seem to list any online retailers. I tried Froogling the UK and German sites but to no avail. Perhaps it's about to be released and will be here in time for my spring oil change.

I guess we need to fly over to Germany and smuggle some back

My God man, we're in enough trouble with importing foreign oil.

Actually I sent a PN to an Ebay seller here in Germany if she would also have 5W-50 instead of 0W-40. She replied with "congrats on winning the Ebay auction, please send 24Euros to my account xxx". I found that a little strange and never transferred the money. However one week later the DHL guy brought me a nice package with 3 liters of Mobil 1 . I had the email deleted by then and have never heard of her ever since. Nevertheless there was another dealer on Ebay who also sold it, so it doesn't seem to be that much of a problem to buy it over here in Europe. Thorsten Sorry for the bad quality. I had to use the phone to make the shot.

True true. Thorsten, what is a Rally Formula (as printed on the label)?

I've got the same viscosity (5w50) but its not 'rally formula'. Took a pic of the bottle, but can't resize pic to enable posting it.

That's the variant they only sell to goodlooking cool Porsche drivers OR it might even be some marketing BS. The label says: "The world's leading tri-synthetic motor oil for all types of modern cars especially those with high performance and turbo charged engines. Expertly improved with a unique combination of high performance fluids including the SuperSyn (TM) anti-wear system, to deliver faster protection on start up for reduced engine wear and deposits, better fuel economy and excellent high and low temp protection." "Approved: MB229.3;VW 505 00(1/97); Porsche" "Made in EU" Thorsten

Arrrggghhh. I am envious!

munro...here you go: http://resize2mail.com/

Thank you very much Dell, your very kind. Here's a picture then of one of the four 5 litre bottles of Mobil 1 5w 50 I purchased from Super Cheap Auto for Au$49.95 (US$37.34)

munro...where are you located?

Dell, Sydney Australia- I could send you some, but the shipping costs would negate the exercise. Can't you get this? I thought you could get anything money could buy in the good ol' US of A? This viscosity appeared suddenly during the middle of 2005. It was always 5w 40 before that, now 5w 50 is all you can get in this store. My thinking is maybe Porsche in Australia re-thought what is suitable for Aussie conditions where it almost never gets down to freezing and regularly gets scorching hot in summer (e.g Dec 31st was 45degC!), so 5w 50 would be more appropriate IMHO, but I might be completely wrong! -Jason

Thanks Jason. Maybe it will pop up soon here stateside. Cheers,

I still think that Castrol would do the trick but I recall reading that someone mentioned it was only 'semi'-synthetic. I still don't know what that means so until then, I'm running Mobil Supersyn 15W-50. Since the car is garaged, super cold starts is not an issue. And if it ever is some strange day, I'll be sure to let it warm up for a good long time.