Hi,
My Porsche mechanic recommends 15w-40 oil for my 951. It has a leaking oil pan gasket, so I don't want to switch to synthetic. Is Castrol 15w-40 ok to use or is there another commonly available dino oil that I should use? I have been using this since July. I don't track it but drive hard on the street.
Thanks, Josh

 

I'd say try it, but I'd also say change that gasket. The problem is not oil, your gasket is just failing and if you drive your car hard, you should use synthetic. It may suck, but I'd just get down there and get changing.

 

Switch to synthetic 5W50, 10W60 or 0W40 depending on weather / style of driving. Leaks should be fixed and oil is not a fix for blown gaskets / seals. Personally I use Castrol RS Sport 10W60.

 

I recently switched to Valvoline Durablend (synthetic blend) 15W-40. I agree in theory that the gasket should be replaced but after I changed the oil my rear main seal miraculously stopped leaking (at least for now). According to the owners manual 15W-40 (or 15W-50) is clearly the preferred weight oil under most conditions for my NA.

 

Porsche AG periodically updates their list of approved oils for their cars (and sends the updates to their dealerships and the Excellence magazine. As of 2004, they recommend a 20w-50 blend for any 944/951. Their reasoning is that as the cars get long in the tooth, the gap between the piston rings and the cylinder walls will increase slightly due to wear and tear. That being said, a thicker viscosity oil will minimize any leaking through and fouling the plugs. Generally, the thicker the oil, the better the protection. As for which specific companies make the best oil, that depends on their flash point (the temp. at which the oil breaks down), their % of zinc content (for lubrication), % ash content, and a heck of alot more. Follow this link for info and specifications on the brands of oil to use. Bear in mind, synthetics are a different beast altogether, and are still better at lubricating than dino based oils.

http://pacific.telebyte.com/allanw/b...fo/oilfaq.html

Happy reading!

 

well maybe i'm crazy but isn't 15w40 primarily used for diesel engines?

 

I'll never forget the email reply that Bruce Anderson sent me when I had the case of the bouncing oil needle in the Texas heat (with Castrol Syntec 10w40)... He said: "Mobile One 10w40. Anything but Castrol!"
One oil change and 50% of the leaks were solved. Got my attention.