A farm and fleet store in my area (Runnings) has Chevron Supreme on sale for $2.19 a quart, so I decided to use it in the Buick. I had a couple questions about the oil (regarding the GM6094M spec that was absent from the bottle), so I called the Chevron Techline, and the guy I talked to was pretty helpful. When I asked about the warranty, he said that they stand behind their products and that they have a guarantee, though it's rare that it gets used. He told me that Chevron supreme would be fine year round in my climate (5w30) and explained the 5/10W30 rating. He seemed to know what was going on. He recommended changing generally in the 3-5 k range but said to go with the manufacturer recommendation. When I asked him what the difference between CS and Havoline was, he said it was just that the Havoline had more moly. I finished by asking about the oil in general, and he said that it is a "quality, premium product" and that they hear good things about it from people, again, no surprise. But they were generally helpful and friendly and I was glad to have called. Just thought I'd share this info with you all.
(On that note, I got really great service from Mobil's customer service too.)
(On that note, I got really great service from Mobil's customer service too.)