First, I live in Arizona and would NEVER consider using 30 weight oil around here. These so-called economy oils make little or no difference in actual fuel mileage and sacrifice long term reliability. Major car companies (except the Germans) recommend these low viscosity oils so they can report a few tenths better mileage to the US government to help them with their Corporate Average Fuel Economy (CAFE) averages which permits them to avoid Gas Guzzler Tax.
Second, the oil you are using isn't on the the MB approval list. I suspect it's because of the rumor that Mobil 1 30 weight oils are not true synthetics, i.e. they are doing what Castrol did and that is using a petroleum base and calling it synthetic. 0W-40 and 15W-50 are true synthetics.
Third, the two Mobil 1 viscosities that should be used in Arizona are 0W-40 and 15W-50. Actually, 0W-40 could be used anywhere in the lower 48 all year round. In fact, I used 15W-50 Mobil 1 in Minnesota all year round because it has the pour point of a 10W-30 mineral based oil.
Go to Walmarts and buy 15W-50 Mobil 1 in 5 quart containers for the equivelant of $3.70 or so per quart.
Last edited by Bud; 09-01-2003 at 10:18 AM.