freeman

The Porsche factory validates the use of either 0W-40 or 5W-50 in our vehicles. I drive in an area that can hover around 100 F for 3-5 months and rarely (< 5 days) below 40 F for the remainder. My factory-trained technician always complained about my use of 5W-50 in my air-cooled 911. I intend to have him put 5W-50 rather than 0W-40 in my 991 since my opinion is that the former is much better than the latter in hot climates. Surely it cannot be detrimental. I need the opinion of the Rennlist experts. Am I missing something? Am I wasting my time with 5W-50? Will 0W-40 do the equivalent (or better?) job under my conditions?

gt2r

Using a 5-50 over 0-40 will give about 10 degrees more protection at the high end of the temp range. That is the benefit of 50 over 40. The 0 gives lower viscosity at start up, but 5 weight is fine at your temp as well. Personally I blend 10-50 with 0-40,,which is ok as far as Mobil is concerned. This really gives me an oil with 5-45 since I blend it 50/50.
The wider the spread in viscosities the greater the break down of molocules, so sticking with say a 40-50(great high temp running) or 0-10(great low temp start up) would be best for break down of the oil but it isn't good for the overall running of a vehicle, especially at a track

exponential

Normal use : 0w40
Track use : 0w40 is O.K. but 5w50 for extra protection.

rnl

perhaps a third radiator kit may be in order?

SteveFromMN

If I lived where you do and the factory specs it I would use the 5W-50. But I live in Minnesota and it was already down in the 40's the other night.
So it's 0w-40 for me.

SB

I'd stick with 0w-40 because I believe that the engine was designed/tested/tuned/optimized with a particular oil grade/viscosity, and probably a particular brand. The last nail in the coffin for me was that Porsche chose to stick with 0w-40 in the cup car racing series!

kosmo

ambient temp is not a important as oil temp. So if youre exceeding, say 250F, then 50w may be in order.

0w is better then 5w at start up. Heck, in theory, 0w are still too thick.

I prefer 0w-40 as I believe theres more damage being done at the cold end vs the hot end.

WCE

Personally, I think 0W-40 viscosity oil is basically a SCAM dreamt up by the marketing people at Mobil! They probably give the oil to Porsche (and others) for free in exchange for the recommendation and specification of a oil weight that NOBODY ELSE bothers to manufacturer!
Unless you're in the arctic, the 5W-40 oil that most other vehicles use is fine for cold startups, easily obtainable and maybe even more appropriate! (and no, I don't know more about these engines than a Porsche engineer, but I do have an opinion to post on the internet!)

Hammer911

Porsche iManual

http://www.porscheownersmanuals.com/...Topping-up-oil