Originally Posted by BCA
There are many (including BMW if I'm not mistaken) who say that you should always stick with top tier gas. Top tier gas (Shell, Chevron, etc.) has additives/cleaners that keep gunk from building up in your engine. Cheap gas has been cited for all kinds of problems, the most common being poor performance and knocking/pinging. If you Google "Costco gas quality" or something similar you will see all kinds of stuff.
I use Shell exclusively (because it's all over Houston) and have never had any gas-related issues. I just wish they'd take the damn ethanol out...stupid government regs.
Edit: Sorry for the thread jack. We can all go back to spotting M3s now.
I dont see any hard evidence on that anywhere.. matter a fact I know a couple people who had broke down after fueling up with "top tier" gas.. two of them from Shell, lol.. and it was bad fuel..
so who knows. I have never had any problem and I use sams and costco alot, but I also use race track and whatever else is around.