I usually fuel up at Shell or Husky/Mohawk out here in western Canada. I fuelled at Extra Foods gas bar(Lablaws/Superstore Chain) and found an increase in milage in similar conditions. I have tried several tanks since and the increase has proven consistent.
I never gave much thought to off brands before but maybe they are worth a closer look. Maybe all the additives and ethanol make a bigger difference than I thought.
Using E-10 will drop your mileage by ~3.3% (125,000 btu/Gal vs 120,900 btu/Gal) based on just the energy content.
Your station attendant should be able to tell you the E content of the fuel.
If your station does not use temperature compensated meters, the colder the fuel, the more energy per gallon. (Ground temp is fairly stable, In the winter, fuel after the delivery truck dumps, in the summer, fuel before.) I am still trying to get a solid number on the real difference, but it is likely only in the 1-2% range. (Our ground tanks are about 57F here, so the most difference is 30F (15c))
Interesting thought! Once I had a look at this thread I went back to my fuel ups and noticed my poorest return came from Shell. I don't recall a difference in driving style or traffic, so maybe I need to run my own little test with another tank of Shell to see if my 'mileage' drops.
The trucks cannot control the temp of the fuel much, so it is closer to ambient, (depending on the time that the fuel sits in the truck this may not be much of a difference.)
Yes, the fuel is sold to the station by weight. but the addition of 4000 gallons of 75f fuel to a ground tank of 55f fuel will change the temp of the stored fuel. It is the change at the meter that works with or against you. (As little as it does, less than 1%.)
More people avoid 'Fresh' delivered fuel on the theory that it can stir up detrius in the tank. IMO this is filtered at the pump anyway.
They do have filters, and there is not really that much rust in the tanks of most gas stations. (There is also basically no water in gas, otherwise we'd get gobs of rust every time we filled up, and also our tanks would rust.) Just myths that still persist. The fuel density point is legitimate, but a 1% gain in fuel economy is well within the margin of error of tank filling. And that's not really a fuel economy thing, that's just getting more fuel for your money. I suspect the gas station probably accounts for this and gives you less volume anyways.