High miles, hot climate - syn. 10w30 or 15w50

[Suede]

I'm going to switch my 1990 535iM from dino to Mobil 1.

Mileage is 117,000. Here in LA the car will never see weather below 40 degrees, but as hot as 120 degrees.

I did read the previous posts regarding this topic, but most seem to be from cold weather folk.

Any advice in these circumstances?

Costco sells 6 quarts of 10w30 for $23.06, and doesn't sell 15w50.

Suede

[Unregistered]

For LA, you should be running a 5w-40, 0w-40, or 15w-50 synthetic oil. 10w-30, especially M1 which is formulated on the thin side of 30 weight (9.8 Cst @ 100c, 30 weight is between 9.3 cst and 12.5 cst) is to thin. Note that 30 weight oils are only approved for the Big six at tempuratures below about 60F.

If you are going to use Mobil 1 (which is generally considered the best widely available synthetic), I would use one of the above forumulas. If you want to learn more than you ever wanted to know about oils, go to bobistheoilguy.com

[KenB]

Since you don't have to worry about cold starts, the 15w-50 is the oil you would want to use. I get it at wal-Mart in a 5qt. container for less than $20.

10w-30 is too light for the high ambient temps in LA and the high miles on your engine.

[dave b]

I've used 15w50 here in LA for the past 4 years.