Recommended oil for air-cooled Porsche turbo?

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Jun 14, 2003
I own a 1986 Porsche 930 with a 3.3L air-cooled turbo engine. I am trying to decide between M1 0W-40 and 15W-50 for the car. I don't drive the car particularly hard.

I am a real novice in this area but do know that these engines tend to run hot and that air-cooled engines rely on oil cooling more than water-cooled engines. That's pretty much the extent of my knowledge.

The car never gets driven in the winter. Summer temps are in the 80s and 90s. Any thoughts on oil choice? What's more important: the cold start efficiency of the 0W-40 or the high temperature protection of the 15W-50? Thanks in advance.

[ June 22, 2003, 09:56 PM: Message edited by: reed ]
Well-wait for opinions of those who are familiar with this engine but in Pa. I would say the 0W-40 would be fine. Either oil will have no problem statring in the spring/summer/fall in Pa. The 15W would be an issue in the very cold winters in Northern Pa.
Porsche has been recommending M1 0w-40 for all its engines for the past few years. What oil have you been using in your car up until now?
Pete, don't forget that the 911 has had a watercooled motor since '97. reed has an aircooled engine, which will run pretty hot, especially in the summer. I'd call Porsche and ask them what viscosity they recommend for an older engine.
Hr reed and

I think that by far the best over the counter choice you could make would be to use Mobil 1 15W-50. This oil meets all of the latest European specs A3/B3 and B4-02. If you were to use this oil with a reasonable change interval I think you would most likely never have an oil related problem with that motor. I believe that M1 15W-50 is also one of the most popular oils used in the air-cooled Porsche motor. Amsoil 20W-50 would be another good choice but I am not sure it would be the best oil to use in cold weather. Castrol also makes Syntec 20W-50 that is rated ACEA A3/B3 and B4-98 but I prefer the M1 15W-50 because of it's better cold weather performance.

The clearances on any air-cooled motor are large enough that I don't think using a synthetic 15W-50 would give you any trouble unless you were living in the arctic circle. I use Mobil 1 0W-40 in two of my cars but i think it is too thin for your Porsche.

Another choice would be to use a HD fleet oil that is an API rated SL/CI-4 15W-40 motor oil. 15W-40 is on the list of approved oils for the air-cooled Porsche motor. This would be a good cheap alternative to synthetic oil however if it was my car I would only use a synthetic oil.

I would stay away from any of the cheap 10W-40 and 20W-50 "dino" oil. With such an expensive car I would not try to save a few pennies on oil.

[ June 23, 2003, 01:05 AM: Message edited by: Sin City ]
M1 15W50 sounds better than 0W40 for air cooled in PA (ever get to Williams Grove racetrack?). Mobil Oz website has Superdrop 25W60 dino for this engine. Motul 300V, Redline 5W40, and I hear Amsoil have a good 25W50 if my memory is correct? IMO don't use dino with turbo particularly air coled turbo.
I think you will get significantly less engine wear using the M1 15W-50 verses the much thinner 0W-40 oil. I just noticed that you stated you will not drive the car in the winter so I can see no advantage to a low viscosity oil in an air-cooled motor. You would likely notice higher or possibly even much higher oil consumption with the 0W-40 or similar viscosity oil.
Reed, I agree with Sin City - the M1 15w-50 is THE choice

The 911 engine is unique with its dry sump.cooler arrangement

An April '92 the Porsche Service Bulletin No 9207 covered oils for all model of their cars. It was specific and indicated oils that prevented carbon build up which had occured in certain areas of the USA

Then, they recommended various oils from 5w-30 synthetics to 20w-50 minerals

The 15w-50 mineral was temperature "ranged" from 0F to 100F> the 10w-50 synthetic had the same range
The 5w-50 synthetic had a range from

Mobil was recommended in that Bulletin and Mobil 1 15w-50 is well received in Porsche circles

I have an '89 928 S4 V8 ( coolant cooled ) and I use Shell Helix Ultra 15w-50 synthetic

Porsche changed to a factory fill synthetic - M1 5w-40 - in August 1992, for all engines. They now fill with M1 0w-40

Last fall, visited local Porsche shop. Mechanics said they use M-1 0-40 for the NEW Porsches and the 15-50 for the old models...guess you would be included in the latter...
Thanks very much for all the good advice. I guess it's pretty much unanimous. I am going to go out tonight and pick up two cases of 15W-50.

Up to this point, I have always used whatever the Porsche dealership recommended for the car which I think was a dino 10W-40. They continue to recommend this oil and only offer the 0W-40 in synthetic. The car doesn't get driven much and I was concerned with leaks with the 0W-40.

Thanks and I'll let you guys know how this oil affects my oil temps after I''ve put some miles in.
I just figured out how to post a pic so I thought I would give it a try.


[ June 23, 2003, 05:38 PM: Message edited by: reed ]
Beautiful car. There was a triple black Porsche 911 Turbo here in Connecticut with the vanity license plate "TURBO". Haven't seen it for a while. I used to own an older 911, non turbo, and they are incredible cars.

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