I recently got back from a trip to Toronto and recorded the best fuel economy ever on my turbo SAAB--35 MPG! (around 500 miles on 14.28 U.S. gallons of gasoline)
This was achieved on Mobil 1 0W-40 at speeds of 70 to 90 mph (mostly around 75 mph though). The oil had about 1,500 miles on it so I don't think that it has "sheared down to a 30 weight" yet, which is a common criticism of this oil.
The '02 SAAB 9-5 AERO is EPA rated 31 MPG highway and my car is exceeding that by a healthy margin.
Another person on a SAAB forum I frequent reported a significant increase in fuel economy after switching to Delvac 1 5W-40 (from Mobil 1 10W-30).
So I find it VERY interesting that xW-40 weight oils, and now also, an xW-60 oil, are providing enhanced fuel economy.
VERY interesting! So is xW-20 really necessary?
Jason
[ September 11, 2003, 12:57 PM: Message edited by: quadrun1 ]