bpu699

I have heard this many times... but what is the rationale?

The oil serves the exact same purpose... It oils the exact same parts.

The newer cars have water cooling too, I get that...

But how is 4 quarts of oil in a 997 at 270 degrees lubing the camshaft/bearings "ok" when 12 quarts of oil at 245 in a 911 is "panic mode" ?

Not arguing accepted oil mythology here, but truly don't understand...


The oil doesn't know which car its in, or what cam/journals its oiling.

The oil is what it is, at the temp it is, when its oiling the motor...

Hows does a 270 degree oil lube better than a 245 degree oil?

txhokie4life

I wonder if there is anything to the effect of the basic engine design.

Engines have been designed to run hotter for better efficiency and emissions.

One of the reasons that I have understood Porsche moved away from air/oil cooled to water cooled. However I am not an engine designer -- and something tells me this is an oversimplification of the reasons and differences between engine types.

Mike

stronbl

^^^^ I'm in this camp too. Although I rarely get as high as 270 degF, maybe 260 degF (I guess it's close enough). I've had many immediate after track and 1 month after track samples sent to Blackstone over the years (same oil type in all cases, M1) and my baseline versus track analyses have always come back nearly identical so I see no unusual wear or protection degradation to the oil. I do, however, always have freshly changed oil prior to any DE / track event.

This is for a stock 2010 3.8L C4S PDK with X51 including 3rd radiator running at all the NorCal and SoCal tracks throughout the DE calendar year / track season.

TXE36

Not an air cooled expert by any means, but oil in an air cooled engine is a defacto part of the cooling system. The oil temp limit in an air cooled engine may be limited by more than just the oil itself. In a water cooled motor, things like cylinder head temps are more controlled and moderated assuming the coolant temp is staying within reasonable limits.

-Mike

stownsen914

Air cooled motors can probably be better termed "air and oil cooled." They depend heavily on oil cooling to maintain cylinder head and piston/cylinder temperatures, whereas water pumpers of course have the water coolant system to manage that. So in an air cooled motor, if your oil temps climb, it not only impacts lubrication but also longevity of top end components, and can negatively impact horsepower too.

One more thing that may play in (and I'm speculating here) is that newer engines are also designed to run tighter tolerances, so may not be as sensitive to thinning of oil due to high oil temperatures.

Scott

Hatzenbach

All good info, thanks

SO I will change the oil and switch from Mobil1 to Amsoil or Redline

When I installed the screens in front of my radiators I checked that there's no debris between the A/C condensers and the actual radiators

What are my options to bring the temps down?
* GT3 heat exchanger?
* PDK transmission cooler?

Mahler9th

I suggest pinging some local resources on this. Several shops come to mind. We have a lot of folks that can likely help you find solution(s) based on experience with your type of car an application.

I would not change from Mobil 1 to some other oil based on a forum posting.

I might also ping the PCA national tech team.

One of the team members is local and used to run the PCA tech team. He may be a good resource as well. He is the #1 tech at Rector and thoroughly familiar with these engines and with racing. He is an PCA-LPR member. If you check out their web site you can read about an upcoming (Saturday) social event where he will be present. You can even score a brat and pretzel at this event.

Frank 993 C4S

I am not familiar with 911s but I would park my Cayman if oil temps ever exceeded 275 deg F (just out of abundance of caution). I run in 100+ deg heat and my oil temps never get above 265 deg and my water temps never exceed 220 deg F.

Mobil 1 is definitely NOT the right oil for what you are doing. I run Driven XP9 but the other suggestions above are good too. Talk to a local race shop to see what others are doing in cars like yours.

I am surprised that your PDK did not go into limp mode at those temperatures and without a cooler. I would seriously consider a Transmission Cooler and adjust my driving to manage the engine better thermodynamically. From my experience racing, you can draft somebody on track in a Miata all day long but in a Porsche you need to more actively manage your cooling by making sure your radiators get undisturbed air every once in a while. Also, turning on your heater inside the car will help.

rbahr

At ~300deg f, the bearings start to become 'plastic', what this means is that they will deform under the right/wrong type of stress. Interestingly, some of the better oils will continue to work at these temps (at least this is what the folks at Redline have told me).

If it is possible to measure it, do so near the hot points.

Ray

chartersb

Whatever else you do, use the best oil you can. If it's Mobil 1, make sure it's their "For Track Use Only" Racing Oil, not the Mobil 1 you find at WalMart and other retailers.

white924s

Just to add one more data point - my 981 will run 220+ on the highway (out of sport plus mode). In sport plus mode, an extra fan kicks in to bring temps down to 198-200. My understanding is that Porshce designed the system this way to get better fuel economy (outside of sport plus mode), and in sport plus on the track, I've seen oil temps up to 235-238, but I don't get worried about it.

tcsracing1

I gave up on Mobil 1 and switched to Liqui-Moly

the_vetman

Everyone will have an opinion regarding which oil to use, but IME Mobil 1 5w-50 is just fine for heavy duty tracking. Done many oil analyses on THOUSANDS of track mile samples (3,000-5,000 mile samples and they kept telling me to go longer). 38,000+ miles (mostly heavy track usage) and engine was just fine.

OP, you need a PDK cooler. Ask John at BGB and he can tell you all about the trouble with keeping PDK cars cool.

mark kibort

Mike
Thats being a little and blind to marketing of the oils sold do us in the market place. as well as discounting this lists actual experience. a "shop" isnt always at the track, or in the car seeing oil break down issues.. (although some are) The OP was concerned about 280 temps. yet many of us that have been racing for 10-20 years have done a lot of experimenting with the comparisons of oil. swithcing oil based on someone that saw major reduction in oil pressure at hight temps, is not too bad of a move. especially when others have seen the same thing. sure, will it work for most and no cause a problem in most cars, sure.... oil is like that. But, if you are concerned and want a step up to something that doesnt break down when things get hot, there is nothing wrong with going to a better quality oil. no different than someone saying these tires have more grip, last longer, dont heat cycle out, or this car handles better, etc.. get the idea? thats what makes this list so valuable.. we get real life experience noted here. THEN, we can look at the circumstances or conditions that the tests/eval were under, and make our own decisions.

my test(s). mobil 1 , buttonwillow, 928....... oil pressure light on at every tight turn on the track, and when RPM was below 3000rpm at 260F.. change the oil to redliine... later Amsoil... oil at 5 bar (max pressure) consistently, no variance. this was true for multiple cars that year. if that isnt an indication of some weakness of an oil, i dont know what is. might not be a problem for a cup car or others.. i use it in my street vehicle. but on the track, we push things to the limit. no harm in stepping up in quality to be sure.


just fine?? when i saw the oil fall on its face, that wasnt "just fine". look ,in many cases this is true. and many cars might not notice a difference based on their design. But, every car will hit a limit and my feeling is that the better oil will always extend that limit. oil analysis doesnt tell the entire story, such as what the viscosity is when at high temp.... all it tells you is that the additives and rated viscosity is present and what other things are suspended in the oil as to whether it should be changed or not. (or what could be wrong with your engine... what parts are starting to fail) this has nothing to do with the protection, in a race car at the temp limits.
I do an oil analysis every other oil change to make sure the engine is in good shape.. often, its very dirty and the lab says, the oil is perfect go on and use! BUT, dont, because 3 -4 race weekends, high temps and all sorts of contaminants are not great for the engine that is racing at the limit. so, i change it as a precaution. cheap insurance.

g-50cab

at 250 degrees - most commercial available oils start to break down and lose their viscosity. They don't recover the viscosity when they cool. This can affect the bearing surfaces and the ability to properly float running surfaces.

I'd recommend an oil analysis (which will tell you what's going on with your engine) and I'd also recommend more frequent oil changes if you are seeing those temps. It's really cheap insurance until you can come up with come better cooling solutions.