Hi. I have a 1987 911 Carerra 3.2 (non-turbo). I have always used Fully Synthetic 5-40 without problems, as was the recommendation of the previous owner (an engineer,who had re-built the engine).
However speaking to fellow owners, it has been suggested that this is a bad idea and the car should be running on something 'thicker' such as the old multigrade 20/50.
This is indeed what is 'recommended' in the original handbook - but bearing in mind 'Fully Synthetic' oils were not available 27 yrs ago !
So...What should I be using ? Informed answers appreciated.

 

I switched to Brad Penn oil. Made for older air cooled cars. Runs cool and uses less oil.

 

Is there a problem you are trying to solve? Does the car use excessive amounts of oil? If not, stick with the synthetic. It provides better protection on start up and is thermally a lot more stable, this is something that could be important in an air cooled engine.

 

No problems just observations. Brad Penn oil is a semi sinthetic oil.
Features

Semi-synthetic
Deliver excellent shock load and high temperature protection
Reduce internal friction for increased horsepower output
Contains strong detergent, dispersant and ZDDP anti-wear additives to help protect critical engine parts

If you look at the 100s of oil threads it is recommended often with no issues identified.

 

use the 10w-60 porsche classic oil.
great broad coverage for cold starts and long hot runs.

 

Thanks for all of you.

 

Just seeing this thread... I have had total faith in Rotella for my air cooled motors. It keeps them well lubed and resists "seeping" synthetics can encourage.