104 degrees in Texas, is 0w-40 stil OK?

I have an issue with Porsche insisting Mobil 1 0W-40 is the oil to use. I called the dealership yesterday and asked. They said they use Mobil 1 0W-40 regardless of the outside temps. Here in the Houston area, temperatures have been around 104 F during the afternoon. Isn't 0W-40 too thin?

Knowing this will start an argument; 0W-40 Mobil 1 is too thin at 68F, much less 104F. Move to an ACEA A3/B3/B4 rated 10W-40 such as Castrol Syntec (recently renamed “Castrol Edge with Syntec Technology).

I was able to find Castrol Syntec 5W-50 at O'reilly Auto Parts, so I bought the last 10 quarts.

5W-50 is good, but the 10W-40 Syntec is better............

It gets triple digit in Sacramento too. Last november I got my first 911 (996 C2 6sp coupe). I immediately changed the oil with 0W-40 and now am coming up on another oil change. I will using 5W-40 this time around.

Motor Oil Viscosity Grades Explained in Layman's Terms understand a little bit first. Then let the melee begin. You can always check your owners manual. iirc, porsche often has a page about oils and recomended viscosities based on use and outside temp ranges. (at least in my 944 manual it does). Recall that in a watercooled 911 (vs an aircooled 911) the purpose of oil is protection of metal. It is NOT also the "coolant" like in the aircooled cars. Your car has water jackets, radiators and a separate cooling system to keep the engine in its correct operating range. Now, if you were in an aircooled 911, I'd recommend a "50" oil. Could be that at 100 degrees, 40 or 50 would be adequate protection.

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Why? Isn't the 50 high side better in 104 degrees?

Initially, yes; but with time, oils with wider weight spreads tend shear down more quickly, particularly under high heat loads, reducing the hot weight (read viscosity) more quickly than the same brand with a narrower spread.

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By going to 10W-40 all you have done is raised the viscosity of the oil at start- up. No change has been made to the viscosity of the oil at engine operating temp where you might want a heavier oil. So if 0W-40 is too thin so is the 10W-40 at engine op temp. The article that racer suggests is good reading and there are many others that go into oil viscosity in more depth. Lot more to it than just the oil weight.

Not quite correct. Yes, going to 10W-40 oil (specifically Castrol’s new version of Syntec) does raise the low temp viscosity while maintaining the higher temp vis, but experience, and several hundred used oil analysis, have shown that: 1. While a 40 weight hot viscosity is plenty for the poster’s ambient temperatures, Mobil 1 0W-40 shears down to very thin viscosities, often in less the 2K miles of use at even moderate conditions. So what started out as a 40 weight hot viscosity ends up being more like 20. 2. Oils with more than 25-30 points spread between their low temp and high temp viscosities tend to shear down significantly faster than oils with 30 or fewer points spread, and then tend not to recover. This requires more frequent oil changes in order to provide any protection in the heat. Unfortunately, none of the oil companies talk about this. 3. Brands do matter. UoA’s have consistently shown some companies invest far more in their marketing than they do in their products. 4. Ratings matter. Ever since the API moved from being the technology and specifications “gatekeeper” to being the public relations and lobbying arm of big oil, manufacture’s are allowed to in-house test and certify the ratings their own products, and we totally ignore their ratings system. ACEA on the other hand requires that oil vendors become signatories to a technical concord agreement, and then submit only finished products to independent lab testing in order to receive ratings. Unlike API, who allows substitution of components without retesting, ACEA requires much more stringent testing and resubmission if anything in the formulation is changed. This is the reason that several Mobil 1 products totally lost their ACEA ratings; they were reformulated, and not for the better. 5. Several companies seem to outright lie about their products, assuming you are dumb enough not to notice. More than one “marketer” of so-called high performance oils imply that their products “meet ACEA requirements”, or “are approved for ACEA applications”. However, a quick check with ACEA shows that these companies are not signatories of the testing concord agreement, and therefore could not even submit their products for testing, even if they wanted to. A couple of these firms (names you would recognize) have been called out in public on these issues, only to then state “ACEA specs are very expensive to acquire and are not particularly meaningful in the markets they serve.” Yet they continue to use deceptive marketing practices designed to make you think they hold ACEA to sell what testing shows to be inferior products. If you thought that email from some guy in Nigeria about the fortune you just inherited raised the “caveat emptor” hairs on the back of your neck, you should look into motor oils more closely……….

So JFP.... Living in triple digit Sacramento, I'd be better off using a 10W-50 rather than what I was planning on using (5W-40)?

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Let's say your post promoted further discussion not an argument. I'm not sure if I was incorrect or just not as complete in my response but in either case your points add more information for the OP to ponder. As for Mobil 1's specs, the following is directly from their website. "Does Mobil 1 Extended Performance meet GF-5 specifications? All viscosities of Mobil 1 Extended Performance meet GF-5. Additionally, they meet or exceed the requirements of various ACEA (European) specifications." I can't say whether they are misrepresenting their product or not but it is what it is and as such I can only assume their oil meets the standards you note in your post although the phrase ".... of various ACEA specifications." might suggest they don't meet all of them. Some of what I have read about engine oil for water cooled Porsche's and their effect on IMS life suggests that change interval is as important as choice of oil when responding to concerns about IMS lubrication and it's effect on the life of my engine. But I will admit, the more I read about oil the more skeptical I am that I'll ever find the perfect oil.

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If you meant "10W-40", the answer is yes as the 5W-40 will fall out of grade in fewer miles.

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To the credit of Exxon Mobil, they are upfront and honest on ACEA ratings; when they have them, they list them. But sometimes the ratings change and the ACEA ratings change or totally disappear; and when this happens, no notice is given, it is up to the consumer to spot it. At this time, wouldn’t label them as deceptive, particularly when there are other more blatantly deceptive advertising used by other oil “blenders”. To put Mobil 1’s marketing dialog in perspective, their 15W-50 oil, long a mainstay with the air-cooled Porsche crowd, lost all ACEA ratings around 2005-2006, and only recently regained them. At the time, they switched the color of the cap on the bottles so they could be recognized on the shelf, which tipped off astute consumers that something had changed. I still have a couple bottles of this product, and it clearly lacked any ACEA ratings on the packaging, as did the tech sheets. They lost them due to reformulation away from Group IV (PaO base rather than esters) blending stock base to a Group III base, and eventually regained them after another reformulation to Group III+ base stocks. When they reformulated the “old” 0W-40 Mobil 1 away from Group IV stocks, rumor has it that it took several reformulations and retesting before the new product made ACEA A3, B3, B4; and then only just. My problem with Mobil 1 is that post Exxon’s acquisition; nearly all of their products have been lowered in performance capabilities, but not in price. There was a time when their 0W-40 was a long lived oil that stayed in grade for many miles under high temp/high shear usage; perfect for a water cooled Porsche. What you currently can buy is a faint shadow of the old Group IV oil, and shears down way too quickly to be used in an M96/97 engine. If you want to really get into “What happened to Mobil 1”, jump onto the BITOG website for hours and hours of technical reviews of what the line used to be, and what it is now.

Crap! The Castrol 5W 50 oil I bought is not Porsche A40 rated, so I returned the 10 quarts and exchanged them for 10 quarts of Mobil 1 0W 40............... I just can't put oil in my Porsche that is not approved of by Porsche.

Much like their “N” rated tires, I wouldn't place that much credence in their "approved" oil list; I’d focus more on which oils perform best, and do the best job of protecting the engine..................

I find it interesting that Castrol Syntec boasts 8X better wear protection than Mobil1 in TV commercials & I have never heard of Mobil 1 disputing this & the ads still run.

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Just curious, JFP: what is your basis for Castrol 10w-40 over 5w-50? Is it because the "spread" is higher with 5w50 thus the 5w-50 requires higher change intervals over the 10w-40? Or are you stating this because of formula/experience/analysis reasons? Thanks as always for picking your brain.

Side by side UOA analyses of both weights have shown that the 5W-50 will need to be changed sooner than the 10W-40 under equivalent usage (temeratures, street, street/track mix, etc.). Oils with very wide weight spreads simply do not hold up as well as similar weights with narrower spreads, probably due to differences in base stocks and the additive packages.

Not to beat a dead horse as it seems with each new oil thread, but the 50 weight Castrol oil - despite requiring changes more often than the 40 weight - in theory offers better protection for engines with larger clearances (older) and/or higher ambient running temperatures (hot summers). Correct?

Up until it shears down to the equivalent of a 40 weight (or less) at the same temp........

Can the shear down be quantified in xxx miles on a normally daily driven engine? Has anyone used Pennzoil Ultra in these engines? During my last oil change, I took apart the oil filter and found a very small piece of some sort of debris (using mobile 1 0W-40). Should I be concerned?

Not to a tight value because each car, driver, and ambient condition is different; yielding differing results.............

fastsvo, What model 911 do you own? Is it a 996 (2005 or earlier) and if so have you had your IMS bearing updated? If the debris was metal then it is possible you may have the beginning of an IMS (intermediate shaft) bearing starting to give way. Speaking of Penzoil - Does anyone really believe that Ferrari approached Penzoil to put their oil in a Ferrari? I'm sure Penzoil had to come up with a very good formulation to pass muster with Ferrari but it all comes down to marketing.

It's a 2007 997 S. So far, I have been changing the oil every 5k miles, since I feel every 15k OCI is a little too long for my taste (and that I don't drive the car often).

fastsvo, On your next oil change, swap out your oil drain plug for a magnetic oil drain plug (check out LN engineering to source one). They are a great idea anyway and you'll be able to tell if the material is metal or not. Keep inspecting your filter and stick with the 5000 mile oil change interval.

I'm on my iPhone so I won't go into this deeply, regarding air cooled 911's. 1. Oil temp and coolent temp are different. Thou the liquid cooling system does help in controlling the temps. 2. Age and How you drive are factors. I own a home out in Palmsprings. We get 120 deg F days. Thou here in CA we can have chilly mornings, it's at this point that you want to get oil to key areas and quick. 0-40 is typically in my opinion a wide spectrum oil used for daily driven cars. If you go gung-Ho and add a have tight tolerances and high viscosity you can place stress on your rings. Not all lubricating systems are designed to handle high viscosity oils along with pumps to add. As mentioned most 911 manuals have a recommended spectrum ambient temp to viscosity ratio. If your very concerned contact Porsche AG / NA for an official reply regarding. Or trust your specialist. Unless you are railing your 911 in 104 deg ambient weather the 0-40 is fine. " Note : I ofcourse do recommend you change your oil / fluids after any track weekend. "