I also have a 2003 Escalade that has a 10:1 compression ratio and calls for regular gas. It has been burning regular gas for 90k miles. The M103 has a lower compression ratio of 9.2:1 and requires premium. I have to wonder how a 10:1 engine can run fine on regular but a 9.2:1 needs premium. I know it is only about a 10% savings, but people will spend a lot of effort and money to try to increase their gas mileage by 10% (20 vs. 22). I don't mind buying the premium if it really makes a difference. However if it doesn't really matter why waste the money.

Sometimes I wonder if expensive car companies specify expensive maintenance or fluids because it seems more exclusive and the original owners probably didn't care about the costs. I would guess that none of the diesels specified veggie oil, but a lot of people are using it.