Originally Posted by PratoN
You're killing me.
EDIT: I think everyone really should shop around, though. I've found a Thornton's station in Illinois nets me 38-39mpg per tank on 93 and then I fill up at the BP and my gas mileage instantly drops to 33mpg. It's happened more than once and I think it's more than just a coincidence / weather / driving style changes.
That's the thing, there are big variations in gasoline octane quality between different stations and I don't necessarily mean between oil companies. I noticed that way back in the 80s when I had a VW GTI with a spark knock ignition. That car would vary the ignition timing alone but you could tell when you put premium in it because it would run better. Often times when you put premium in, it didn't run better so you knew that station was cr@p. Going even farther back, when I worked in a gas station they would often top up the premium tanks with regular when they ran out of premium on the delivery truck. So to me if I pay for premium and the car is not noticeably running better that station or maybe the distributor is dishonest. Sure there's other variables too like summer/winter gasoline blends but that variance you saw shouldn't happen going from one station to another in the same general time period.
Lest anyone think this thread has gone astray talking about gasoline, it really hasn't because it is now talking about driveability problems that the DCT is often blamed for but may not be directly attributable to the DCT.