[John_AZ]

I have been using Castrol GTX 10-40 winter and 20-50 summer for years in both cars. I use either the Porsche oil filter or the Mahle-both have the correct oil valve to prevent draining of oil in filter when shut down. Keeps oil pressure up on critical startup. I change the oil at 3K or 4K intervals. I've had no problems.

NOW, Castrol has lowered the amount of Zinc-ZDDP to .12% from what I have found. Racers on the 911 board and others swear the Castrol GTX oil is crap and foams-under severe driving conditions. When it foams the rod bearings fail. BTW if your car has 100K to 125K mileage=replace the rod bearings anyway.

I will go with a Valvoline RO. Redline or do further research in the future.

GL
John_AZ