15W50

A common topic of debate, when I took my 01 C2 in for the 75K service, the mechanic said we are going to switch you over to 15W50... This was at Rennwerke in Elmsford, NY. Looks like Jim (1999Porsche911) is on to something..? Ross

Uh oh - now you've torn it! That's going to put a bug in the eye of the 0W40 crowd Chris.

[QUOTE=rcg412]A common topic of debate, when I took my 01 C2 in for the 75K service, the mechanic said we are going to switch you over to 15W50... This was at Rennwerke in Elmsford, NY. Who died and made this guy the oil expert? Everybody just do what you think is right and kill this topic before it gets legs....again

What about blending 0w and 15w to make 7.5w... a ceasefire/compromise between these two warring tribes?

I've got the whole thing covered. I drained the oil and put Prolong in the sump.

I'll make extra popcorn for those who want to sit back and watch the fight!

OK to get the fight going...15W50 is water...and it s not recomended by Porsche...now...some popcorn please.

I have an early Boxster. And NONE of you stone throwing 996 folks were around back then. We used Mobil 15W-50. Porsche said to use it. The dealer used it. I still use it and I have a 9 year old car. Proof is in the pudding, at least where I live. And 7 years later on the various message boards and attending the local tech sessions, I have yet to hear of a single engine problem related to the weight of oil. For popcorn, I hear peanut oil works, but I do not know the weight.

Wrong! This 996 owner was a Porsche owner long before the Boxster was even invented and this oil grade/weight discussion predates the Boxster by at least 7 years with the introduction of the 964 series, along with: a). The switch at the Porsche Factory from Mineral (Dino) oil to Partial or Full Synthetic oils which occurred in 1989 and b). The discovery in the 1980s (circa 1986 onwards) that American manufactured oils were causing coking problems in many Porsches delivered to the USA. This resulted in the first of many overhauls of the Porsche (as in the Factory in Zuffenhausen not the PCNA or Dealers) oil recommendations and manufacturers approvals for use in 1989. Personally I don't give a toss what oil anyone uses in their Porsche, but for new owners of any Porsche be it air or water cooled and under new or used warranty, I recommend you follow the oil recommendations provided for your model in the owners manual and try to keep up to date with the "Approved Oil Recommendations" issued periodically by Porsche. After the warranty has expired and you feel comfortable deviating from these recommendations based on "Porsche Owners" experience written on various internet forums, blogs or magazine articles then that is your decision. As for the statement: I would love a dollar every time this kind of statement has been used to justify any position in an argument. The reason that this statement can be made is that nobody has every bothered to investigate if there are any genuine advantages or disadvantages when using thicker oils. What I can say is that data is being collected about various engine problems versus oil grade and weight from around the world to see if there is any relationship between the oils used and common Porsche engine problems. This is being done for aircooled and watercooled engines only for the 964 to 997 series of 911 at this time. Somebody else can do the rest. This will take quite some time to put together, but I am looking forward to seeing where this leads, if anywhere, but we will never know until we try. For the record I use 0W40 because of the temperature conditions in Switzerland, but I would never consider using thicker oils anyway. I like my oil to flow when I start a cold engine, but that's just me. I have only ever used 5W 30 and 0W 40 in all my Porsches. Once I had to top up with a slightly thicker oil on a visit to the UK because what I wanted was not available. Ciao, Adrian

Wouldn't it be the case that at temperatures at or slightly below freezing (down to -10 degrees F), both oils will operate about the same (check the chart below)? Indeed, the guys over at Car Bible offered the following which makes a ton of intuitive sense: Most 5W oils have a pour point at -40�F (-40�C) The base oil is the same in 0W40, but it's pour point has been lowered even further - sometimes to as much as -50�F (-46�C) Pour point is 5�F above the point at which a chilled oil shows no movement at the surface for 5 seconds when inclined. This measurement is especially important for oils used in the winter. A lot of manufacturers tend to quote pumping temperature rather than pour point. Pumping temperature is the temperature at which the oil will pump around the engine and maintain adequate oil pressure. This is typically 20�F above the pour point - ie. 25�F above the point at which the oil is basically a gel. So 0W oils don't flow through a viscometer in zero seconds - they rate at 5 seconds like a 5W oil, but they will be pourable at a much lower temperature. The bottom line then is that if you think your car is ever likely to see a cold morning in the -45�F (-43�C) range, you should be considering 0W40 oil. If not, 5W40 will do. Note that at -45�F, you'll probably have more to worry about than your engine oil - like your radiator fluid, brittle tyres, frozen locks, permafrost on the windscreen etc.etc.etc....... However, I think that the reason Porsche uses the 0W-40 instead of the 15W-50 is because the 996 motor has a lot tighter clearances than in past motors. Thus the lower weight oil reduces friction and drag in the motor and thereby increases horsepower and fuel economy. But, I don't think that anyone is going to have any problem using the 15W-50, particular in climates where it never gets below freezing (indeed, I use it in the summer months here in NYC). Indeed, I've read that for sustained high load, high temperature driving, it's preferable ( click here ). But, unless you're beating on the car regularly, I'd likely stick with the 0W-40 year round unless you call Miami or LA your hometown (ah, sun year round...what a life) or track your car a lot. Indeed, that's what I'm going to do this winter, after researching this issue the past few months, and stick with the lower 0W-40 weight next summer. And for all you guys who get tired of these wars, then stop reading. The reason that they continue is because a truly objective conclusion has never been reached...hey, just like in the Middle East.

I looked in a 1999 Owners Manual, and a 2003 Owners manual and BOTH manuals recommend 15W50 in >50F and <50F temperatures..... So if the manual is wrong, why didnt they change it in 2003. Ed's chart makes an excellent point... the 15W weight is essentially identical in >-10F! What I have observed is that the 996 runs HOT (especially 99-01)... and as my temp gauge in nyc traffic creeps right of 180F, the oil pressure drops... a lot, easily seeing 1-1.25bar, only when temp is normal does the oil pressure rest at 1.5... that thin of oil cannot be good in the long haul. Ross

Ed, I use 0W40 because 5W30 is no longer available from Mobil here. I stick with Mobil because they provide a one year guarantee on all their products if you use them during your service. I have read all the data you have posted many times before. They are full of theory and devoid of practical facts. This story will never be solved until practical experiments are done on real engines and real wear comparisons made. One important fact is that the data presented in your post and in the one from Ross presenting his owners manual is that it "only" applies to the USA. My German owners manual has a completely different set of oil recommendations with the thickest oil recommended for Summer being 10W 40. 0W 40 is recommended for both summer and winter. 15W 50 is also not available here either. I have not seen it in other European countries either, but that does not mean it is not around. The other issue is the confusing information coming from Porsche. Their oil recommendations from Jan 1st 2005 which were posted to this forum a while ago, no longer show a 15W 50 oil recommendation for all Porsche models from 1985 onwards. Porsche also say that Mineral oil is no longer approved for the Porsche engines, whereas the American 996 2003 OM lists Mineral oils. This was a huge argument among the 964 owners because Mineral oil was taken off the list here in Europe in 1989, but remained in the USA for over a decade longer. American dealers were receiving their customers 964s filled with Shell Synthetic oil, the 964s were being drained and refilled with American made Mineral oils. This practice continued long after Porsche signed their contract with Mobil at the end of 1992. The Mineral oil guys still go after the Synthetic oil guys to this day just like the 0W 40 versus 15W 50 guys. One other important point which does play a part is that American oils are significantly different in blending and quality as compared to European oils. Let the battle continue, but I will stick to what is in "my" owners manual and what is available. I also never assume to think what Porsche Engineering is thinking, they are German. By the way my main interest in this subject is not necessarily the engine wear issue because this will take years and years to monitor. A project which I completed in my last job as the Engineering Manager for an Airline was to see what was causing chemical build ups in areas of our engines that were found when they were pulled apart at overhaul. We also noticed that our engine oil consumption rates were increasing, reducing our overhaul times. Cutting a long story short, I discovered that not all oils were oils, not even from the same manufacturer. The additives used were different and one manufacturer and one of their brands was particularily bad. We also found that some oils were killing seals faster than others. This took five years to complete and my interest now is with the Porsche Secondary Air Injection systems (CEL). How the ports get clogged up with burnt oil residue and which oils cause the really hard, have to drill blockages and which ones if any don't. I am sure that the Synthetic blends of oils we use in our engines contribute to such issues. Ciao, Adrian.

Just my own observation. I ran 0-40 until this summer when I tried 15-50. I experienced start up lifter clatter with the the 15-50 that was not present ever with the 0-40, which I switched back to shortly after.

JB, This is one of my concerns. This first showed up on the 993 when they fitted hydraulic lifters. Not an issue when everything is nice and warm, but an issue when everything is stone motherless cold. These are the things that lab rats and their tests never show up. One argument about using thick oil is that it sticks and stays. I have not seen any verifiable genuine evidence of this so to me it remains a theory. I am also concerned about over pressurising my oil system. In an emergency once many years ago back in Alice Springs I had to add some aircraft engine oil to my old beater. It blew the oil cap clean off and left a nice dent in the front lid. not that I expect Porsche recommended oils to do this Ciao, Adrian.

Adrian, those are two VERY INFORMATIVE posts. Thanks for taking the time. Even though I can see the merits of using the heavier weight motor oil, like you, I'm going to go back to using the 0W-40 full time/year round. I guess the point is that Porsche may not know everything, but they sure as heck know a lot more that I do...despite my efforts to educate myself more on the subject. Moreover, I wonder if the thicker oil actually makes the engine work harder and thus wear it down over time rather than prophylactically protecting it as common sense might indicate. Anyway, thanks again for your post.

Yeah, 15W oil is good for New York especially with winter right around the corner......NOT! What a stupid move unless you plan on changing the oil PRIOR to the winter temps coming. If anybody wants some 15W-50 oil for cheap just let me know. I bought whole bunch and decided that I am going to stick with 0W-40.

There was a time when the big 3 US auto makers recomend using 10-40W and the use of 20-50W or SAE 30W. Today many of the big 3 recomend 5W-30 or even 5W-20. Times have changed and so has engine designs. IMO I would stick to the main recomendation of 0-40 or 5-40. I feel the 15-50 may have some start up effects with either the lifter or the varioram components. I will continue to use the thicker stuff for my 930, but my newer car will get the thinner stuff.

I would not use 15W oil in NY, otherwise you might as well fill your rear with Astroglide. Wait that didn't sound... ah forget it.

Alright - I called my mechanic and asked him about the 15w50 in the winter months that it would be too heavy, and he said not at all. He mentioned they are using it in all 996s, specifically higher mileage, and all turbos.... better protection. This guy has been working with porsches for 30+ years... I gotta believe that he knows better than most people here.

Does he know better than the engineers at Porsche? That is the question. And the answer without a doubt is no. Hell, I used to use 15w50 or straight 40 wt too..... in my turbo track car. You know, oil cooled turbo (really hot oil) and moderate to hot temps only. That's some stout oil. I'd just as soon my lifters not make noise on start up in my 996 and actually acheive the factory rated hp, thank you very much. Why would anyone ignore the current manufacturer's recommendation.

I'll make extra popcorn for those who want to sit back and watch the fight! __________________ Tim K. '04 996 C2 Lapis Blue over Gray SIG by Chads996 Tim - That's a good one!!! I'll take a beer too if you have one.

Why would anyone ignore the current manufacturer's recommendation. Maybe because some people have a little more experience with engines in the real world versus some of the desk bound engineers who make these unfounded recommendations. So, let�s review. There are some people who insist on using 0W40 oil because it is approved by Porsche. Their argument, for the most part, is that Porsche knows better than anyone what is best for their cars. Yet, they do not run �N� rated tires which are the only tire approved. They change oil at 5,000 miles rather than the higher mileage recommended by Porsche. They use gear lube that is not approved. They run tire pressures which are not recommended. They make various body mods that affect the aerodynamics of the vehicle. They tune the engine to produce more power than the infallible engineers determined was the best for the vehicle. They fill their windshield washer reservoir with non Porsche fluid, completely ignoring Porsche�s recommendation. They run spark plugs that are not approved by Porsche. I wonder how many use a battery other than one purchased from Porsche? After market clutches and flywheels not approved by Porsche? Wheel spacers? I have to assume that for those who made any of the above changes to their Porsche engineered vehicle must have a certain level of intelligence to have determined the changes would not adversely affect the vehicle. I wonder where this level of intelligence is when those same people run 0W40 only because it is oil approved by Porsche. When people do not understand something, they will always follow the marketing hype.

The factory is OK with both, that is clearly written in the manual and was factory fill. My oil pressures when the car gets mildly hot are very low, which is somewhat unnerving and cant be good for "achieving" horsepower. But I am not a mechanical engineer, or mechanic, so I dont really know for sure. I'm bowing out on this one...

The Best Response Yet!!!

You got it! One box of popcorn and one beer, comming up! No need to tip!

I chose the oil that Mr. Ruf(the only guy that Porsches allows to pull cars off the line, do what he wants to them and put his own VIN number on them) puts in every 996 they service 0w40 For the previous poster, They modify just a few cars a month.

best response I've heard in ages to this long debate. just an fyi....consequently each time 0w-40 has been used in my pcars, I suffer an rms leak. when filled with 15w-50, no leak. coincidence? ok...just kidding! lol heck, I've ihad great results using evo! y'all should try that!

Windshield washer fluid is as critical to the performance of a fine sports car as the oil in it's motor??? If the motor doesn't run none of the other things you list matter at all. I don't know the answer, but it was quite apparent from the previous thread on this topic that you don't either. So that being given, I'll rely on the folks with the best data and who warranty these vehicles (which is the point of specific recommendations like clutches, etc. quite obviously). I apparently missed the "marketing" hype that I was swayed by. TV ads? Print media? Fill me in. >>>The factory is OK with both, that is clearly written in the manual and was factory fill. My oil pressures when the car gets mildly hot are very low, which is somewhat unnerving and cant be good for "achieving" horsepower.<<< Well, actually it is. Put thicker oil in, get less HP out. Ask some motorsports professionals if they run lighter oil for qualifying than for an enduro.

This a discussion about oil and not other stuff. Ok please tell me how many of thoes so called experts actually rebuild 996 engines on a regular basis. Many mechanics go by old time experience with Porsche cars, ie cars that are not designed with todays tolerances or materials. As another poster said Ruf uses 0W-40 may so are you saying he has bought into marketing hype. From my knowledge I do not know any 996 engine that were blown due to too thin oil and if your experts can show proof that it was caused by using thinner oil then I'll believe it. To my knowledge most engine failure on a 996 were due to oil starvation from DOT tires, overheating, or bad castings. You may be right that the thicker stuff may protect better on track engines, but the thinner oil may be better for all conditions. DO you know why Chrysler runs a 5W-20 on their multi-displacement Hemi when the original V8s ran 10W-30? The valve system to turn off some of the cylinders works better with the thin stuff. Their was a time when the recomended oil for the chrysler V8 was not 10-30 and was thicker stuff. Times have changed and so have engines.

This thread is for people to share their opinion of which weight of oil they perfer and why. There are really no right or wrong answers here that at this time are universally accepted, only opinions based on what owners preceive to be important and in their cars best interest. Some makes sense, some nonsense. For some, the reason to use, is others not to use. I have read where some use 0w40 to keep the lifters quiet and others feel it contributes to noisy lifters. I found out a long time ago that because someone in a certain position recommends a certain product, that they may actually know less than I about it. I do know a fair amount about oil, as in my business I build high performance motors and have since the '70's. I have raced at Bonneville, roadraced motorcycles for 8 years using motors (Superbike) that I have designed and successfully built. I have never had an oil related problem or failure. I sell oil, filters and the like, see first hand what works and doesn't and why. Bottom line is, use what you like, as you are probably more difficult to please than your motor. For about all of the lower 48 anything for street use from 0w40 to 20w50 should be fine. Keep it full and keep it clean, thicker w weights will warm up slower and should be treated accordingly. Once the engine is at operating temperature there is very little difference between Xw40 and Xw50 although it was explained to me by a Petro-Chemical engineer that the lighter oil creates less oil sheer (friction) and will remove heat more efficiently.

"Bottom line is, use what you like, as you are probably more difficult to please than your motor." That's the best explanation I've heard throughout this entire discussion thread....except for the popcorn suggestion.

... and all this time I thought oil was supposed to reduce friction!

[Image-only post; no author-written text. Original image references:] https://rennlist.com/forums/images/smilies/biggrin.gif https://rennlist.com/forums/images/smilies/beerchug.gif

I am currently running 75w90 gear oil in my engine. It took me a while to get it started. My thoughts are that with the thicker oil the engine should produce zero wear and i will test that with a used oil analysis like I always do. My strategy is to never shut off the engine, that way I will avoid any start up wear whcih may be present with the heavier oil. Also, never shutting off the engine will save on battery and starter wear. With the engine always running i will not have to worry about seasonal changes either. I'll post my UOA as soon as I get 100 hours on the ngine. Or I run out of gas.

I like the way you think.

I ain't gonna be fooled by marketing hype and evil engineers....

1. My Manual says "Use only engine oils labelled as API SH or SJ, or ILSAC GF 1 and viscosity grades of SAE 10 W-40 or higher." 2. My M5 requires 10w60 at all times or voids warranty. 3. Racers use low viscosity for qualifying and high viscosity for endurance. Need I say more? 15w50 is it for me.

Reviving a hot thread from almost 20 years ago. If this was that contested in 2006, wouldn't 15W50 be even more pertinent now?