[Tool Pants]

All of the above and more is why what oil to use is often debated.

Porsche comes out with a list of approved oils about once a year. 0W-40 was put on the list in 2001. 5W-40 was put on the list in April 2007. The list for 2001 said Mobil 0W-40 was now going to be the factory fill.

Back then 0W-40 was hard to find, unless you bought it from a Porsche or Mercedes dealership. You could not find it on local auto parts shelves. In my area there is a local Mobil distributor who would order a few pallets and that is initially were the local guys got it. Back then Mobil said it was not going to make this a consumer oil. I forget if Mobil or the distributor told me this. Something changed because after a time it started showing up on shelves, but you had to hunt at different stores.

Even before then, it was said 10W-40 was the factory fill, but it was not sold in the US back then. People would try to replicate it by mixing equal parts of 5W-30 and 15W-50, as those oils were sold in the US. In the US Mobil now sells 10W-40 as a "high mileage."

Oil is a funny business. Mobil has the lion's share of the synthetic market. Mobil makes enough money that they can pay manufacturers like Porsche and Corvette for a sticker on the car.