My only point to add to this, is when you throw out that tank, you also throw out the amount you spent, so it affects more than your mpg. As I said before, the impact will be non-noticeable after you have had a few. I have had to get 3 tanks in a row at 12 mpg to actually cause the average to go down from 20.9 to 20.8. Crazy.
Its your fuelly, but still, something to think about.
__________________
|