What weight oil for 1969 911S

[dhopkins]

What weight oil is best for an early 911S? Peter Morgan recommends 15w-40. Someone else told me 20w-50 is best. What would you guys out there recommend?

don
___________________
1963 356B Super
1969 911S
1981 911 SC

[boxster03]

20-50 at least for Southern California

[Steve@Rennsport]

What weight oil is best for an early 911S? Peter Morgan recommends 15w-40. Someone else told me 20w-50 is best. What would you guys out there recommend?

don
___________________
1963 356B Super
1969 911S
1981 911 SC

Don:

If you synthetic oil, use 15w-50. If you use dino oil, use 20w-50.

If you use dino oil and are going to operate the car in cold weather (<40 deg F), use a 15w-40 or 10w-40.

Hope this helps,

[dhopkins]

Steve,
Thanks. What is dino oil? Will heavier oil lessen the likelihood of oil leaks?

don

[gruen911]

Dino-saur as in dead dinosaur (fossil) oil...

[Steve@Rennsport]

Steve,
Thanks. What is dino oil? Will heavier oil lessen the likelihood of oil leaks?

Non-synthetic oils,.... The good 'ol stuff we've used for years.

Oil viscosity has little to do with leaks aside from VERY thin oils can wick themselves out of places you'd never believe.

Air-cooled engines have running temperatures that are hotter than their water-cooled brethern so they need the thicker stuff for when you really lean on the engine.

Remember, the oil temp sensor only samples the temperature at one point in the engine; there ARE hotter spots.

[tom dance]

I always use 20-50. Seems to work well.
Tom

[rgunson]

i faced the same problem having rebuilt my 2.2S engine
be aware that a lot of folklore surrounds this issue
in the end i opted for fully synthetic Shell 5W-40
it is true that syn oils will tend to find their way through old gaskets, however i wasnt faced with this problem as they are all new on my car
an early post states that the air-cooled cars run hotter than water cooled, which is true however, it doesnt mean you shouldnt use a fully synthetic oil
it simply means you should be looking for the second rating number to be as high as possible
to me common sense suggests that you should use the most advanced oil you can get your hands on (assuming you have no issue with old gaskets)
btw - i understand that syn. oil doesnt cause gaskets to 'shrink' per se, but rather mineral oil causes the gaskets to swell. when you put in syn. oil the gasket simply returns to its orig size, which yes, can cause oil leaks
but until someone can explain in scientific terms why an old car needs an old oil i really cant accept such an argument
syn oils are thinner on start-up, and therefore get pumped around a cold engine much quicker than a more viscous mineral oil reduing metal-on-metal time.
then at high temp they maintain their viscosity much better than a mineral oil, which lose their viscosity and become so thin that they are unable to protect the engine
put simply, a mineral oil cannot protect your engine over anything like as wide a temperature range as a syn oil
leaks are the only negative you might suffer
some may say also say price, but in my view if you can afford to run a car you can afford to use decent oil

[SandyI]

I'm sure there are winter days in places where you have real winters where it takes forever to get an early 911 up to proper running temp so perhaps a synth oil may be valuable at start up. But for severe outdoor temperature swings like we have in So Cal (Like the June day I left my house at 5:00 AM in 55 degree weather and found myself running my third 20 minute run session at Streets of Willow in 110 degree heat nine hours later ) 20W50 provides 100% protection for my early 911.

[rgunson]

Oh well if you need a 50 weight oil for the hotter weather why not try the following, which according to the Exxon-Mobil website is sold in the US:

Mobil 1
Extended Performance
15W-50

This gives you the best of both worlds. Recognising that an air cooled engine generates a much wider range of operating temps that a water cooled engine, i think fully synthetic is the better choice. As mentioned earlier, it does assume that your engine is in good mechnical condition - i.e. good compression & no heavy leakage around gaskets/seals.