spiller

Obivously in your case, you have some good results to back up your theory. Whats to say it wouldnt have lasted longer with a life on 5w40 or 0w40 though? The only reason BMW recommends 10w60 for their M3s is because those motors are renowned for using loads of oil. Poor engineering on BMW's part lead to them seeking out castrol to specifically develop a 10w60 that wouldnt burn off by the litre in very short intervals.

I am not an oil expert, far from it. Im playing a touch of devil's advocate here for the good of this thread. The points about higher thermal load have been highlighted by Macster above. I will go on to ask why would you want to further add to the thermal load of an engine which, as you said yourself, already produces quite a bit of heat on it's way to making 100 hp per litre?

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ssigarto

As a former owner of a number of BMWs including an E46 M3 and E60 M5, i can attest that indeed BMW recommended the Castrol 10W-60 oil. I can also mention that as the engines in those cars aged, many of them suffered rod bering failures. A good number of us chose to use Mobil 1 0W-40 in our BMW M cars.

Cheburator

I have a 996.1 CS - my car was the 1st street car in the World to have the K400 kit installed by Manthey Racing at their facility in Meuspath, next to the Ring.

I know this for a fact because the first owner of the car on the German title document was Olaf Manthey. My car was the test bed for the kit - and until I bought it last year was maintained by Manthey Racing throughout its life. The car is on 30,880 miles and 530hrs as of this morning. It has been exclusively run on Castrol 10W60 from Jan 2000. Had it on the Maha rollers at VGS Motorsport in Koln on Saturday - 403hp...

I am kind of thinking here - who knows more about the Mezger? Is it the guy who has won the 24hrs of the Nurburgring 5 times and Le Mans twice and now runs the Porsche sports car racing programme http://www.porsche.com/usa/aboutpors...257C43002FC1B2 or the forum experts???

JarmoL

Interesting piece of history above. My K400 was done in 2003, owned by one of Manthey's racing drivers back then. (he still drives for them)

117 000 km's done now. So nearly 100 000 km with tuned engine. I am using 5w50 Mobil if it matters.. Hmm.. Maybe I should have it dynoed as well.

Cheburator

The engine is so well designed/built, I don't see a reason why it would not last double that provided it is maintained properly.

And contrary to what some in the UK say, they do make their claimed bhp numbers, but just need a proper dyno set up, with the correct air feed to the carbon shroud and cup filter. Dyno-ing a K400 on a standard dyno is a waste of time as the car sucks in air nicely warmed up by the cats and as a result it goes in stupid mode, where it shows 340bhp...

P.S. My car was co-owned by Michael Eschmann - also a driver for Manthey and at one time a partner in Manthey Racing.

mistermct

Thicker oil yields more pressure for a given flow rate. Pressure can be reduced by regulating pressure (as you noted) and thus reducing flow or using thinner oil and maintaining or even increasing flow rate.

Edit: this is incompressible non-ideal fluid dynamics


Pressure relief valve engaged means less fluid flow to engine (some to engine, some to bypass) -> lowered ability to extract heat from the moving parts. This is where higher thermal loads of high viscosity oils comes from. This only applies when there are substantial differences in viscosity which is at lower operating temps...

Edit: Lower flow rate -> oil is in contact with parts longer -> transfer more heat to oil. Assuming this is more significant than shear effects. Could be wrong.
Low flow rate (or higher pressure) applies mainly at normal street temps (and especially lower) where there is a more significant difference in viscosity (SAE grade specs):
40 grade: 12.5-16.3cS @100C; 2.9cS @150C
60 grade: 21.9-26.1cS @100C; 3.7cS @150C

At the 150C viscosities, flow rate and cooling//lubrication effects are very similar between the oil specs.

Mainly track use? At higher track temps (as you noted your use above) most oils will have very similar viscosity at high oil temperatures (>300F). This is likely why you are seeing decent wear for your situation.

Oil is like tires -> needs to be for the right application. Given that many street drive AND track their cars the marginally higher viscosity of a 60 grade vs 40 grade oil at track temp may not be worth the sacrifice of substantially higher viscosity at cold start and normal driving. Almost all oils are too thick at cold start to protect properly.

Edit: Bob is the oil guy has a great summary on oil selection and cold temp viscosity: http://www.bobistheoilguy.com/motor-oil-201/

If many of these are street-driven cars the thinner oil would protect better - flow more and be less "too-thick" at cold temps. Newer synthetics will also have higher film strength than older synthetics/mineral oils and will offer improved protection over the super-thick oil recommendations of 20+ years ago.

Edit: Again with Bob: http://www.bobistheoilguy.com/motor-oil-107/ look at the comparison table of a few of the SJ vs SL test criteria... lower maximum cam wear + lifter specs offers better protection with newer standards and oils. In short... newer oil has better standards of protection.

porschedog

everybody knows Forum Experts have the Best info - they read something somewhere sometime ago on the internet

mistermct

I'll take the bait... I'll go back and add references. Always good to have science support the soapbox.

Kaizu

I am no oil professional nor have strict opinions about the matter.

But if mods and a lot track driving, I would use Castrol 10W60.

I have not found any professional motorsport shop in Europe that has a track record of using these engines in endurance races that would suggest using another oil than that.

I have done 81k kms on track with a 996TT, the car sees only track and some autobahn runs. No ordinary street driving.
Most track driving is on Nürburging so on each lap there's heavy engine load up to 6th gear with full throttle.

Engine is still original even though it has had bigger turbos and more boost since it was _new_. That's crazy amount of hours at full boost.

I give the car extreme beating each time I use it and I don't care at all if the motor blows tomorrow, because still the durability has been much better than anyone could have expected. Mezger rocks!

997rs4.0

What oil do they use in the cup cars?

lax01

Yeah...I'd be curious about this too. Also which Castrol 10w-60 oil are people using? The TWS 10w-60 that the S54/S60 (BMW) use? Do you get it at BMW dealers? That stuff is expensive...

I've been running M1 0w-40 for about 4k miles (1 year worth of time) and I need to switch it soon. Am planning on getting another oil analysis as well from Blackstone when I change the oil.

spiller

Given how regularly they rebuild the engines i'd hazard a guess at whatever extracts the most HP. Would also be interested to know though.

spiller

The TWS can be had by the 20L drum at around $350 AUD. I'd suspect you could find it a lot cheaper than that in your country. Dealer will most likely rape you if you buy it by the liter from them. Not sure why you would want to use this oil in your GT3 though? It was specifically developed to go into M engines that drink oil like its water.

Cheburator

That is another misconception about Castrol 10W60... It started off as Castrol RS 10W60 way before BMW's /// M engines supposedly started to drink oil... Then it was re-branded as TWS, which stood for Ten W Sixty and now it is called Castrol Edge... There have been some subtle changes in the formulation, particularly with regards to ZDDP content, but in general it has been around since way beyond the first engine it had approval for - the S54.

Secondly, as a serial BMW ///M owner I beg to differ on the drinking oil stuff. The 4-cylinder engines do not drink oil at all. The 6-cylinder engines do not drink oil if in good health either. I have had two S54s from new - in a M3 SMG and in a Z4MC coupe. Still have the M3 on 95k miles, sold the Z4MC after 50k miles, of which about 20k miles were spent on track. The first V8 - the S62 drank oil, but then BMW changed the design of the rings and they stopped. The S85 drinks oil, but it is a V10 that revs to 8250rpm, the size of the piston skirts is laughable and it is in a alusil block. What exactly did you expect? FYI, the S85 consumes about 1.5ltrs of oil every 3000miles. About par for the course on a 996 or 997 Carrera engine...

P.S. You all talk about thermal this, thermal that. Viscosity this, viscosity that. Go and read what happens to film strength once the oil is diluted with fuel. Ah, perhaps 10W60 is a lot better at that? And perhaps most GT3s/TT spent a lot more time at WOT than normal?

I am out of this debate as I am really struggling with some people who are armchair mechanics arguing indirectly with one of the most successful Porsche teams globally. Perhaps I should print this thread and take it to Manthey next time my car goes in for servicing so that the wrenches there can have a right laugh?