I just picked up a 1989 Saab 9000CD Turbo to temporarily replace my 86 BMW that I lost to a fire. It's not a brand new car, but I love this little car! Great on gas but the turbo keeps it moving. I am having one problem... Deciding on an oil and weight! I live in Southern California: Summer - 60-105 Winter - 45-70 Here is some info about the car... 89 Saab 9000CD 4 1/2 quart capacity 175 turbocharged ponies 2.0L 4 Cyl. 111,000 miles. I drive it kinda hard and average 24 MPG. It's pretty hard on oil since it's a turbo 4 cyl that runs kind of hot. I think it's got 10W-30 Castrol in it now. I think I would like a thicker oil, but not too thick... I was thinking about this: 3 1/2 Quarts Mobil 1 10W-30 and 1 quart Mobil 15w-50 with a Bosch filter. I think Saab recommended 10W-30 every 3,750 mi. And what about an interval???