This is interesting to see they deliver it at the pump. I'm sure my driving habits have more to do with it than anything but I do feel like I get more variability with my fuel economy at Costco than at Chevron.
Would be interesting to see what BITOGers think is the best gas for fuel economy. I'm sure someone has done some serious experimentation.
The single most important thing for fuel economy is going to be the base fuel. And there's little that the refinery can to do influence the energy content of base fuel during refining, which is going to come from the crude oil. And it may be different a month later when they receive slightly different crude oil. On top of that, fuel is a commodity. It has to meet certain standards, which will include a range for the energy content. I've heard that energy content can vary up to maybe 5%.
The brand at the pump may not even be the same company that makes the fuel. That's not how fuel is transported by pipeline operators, which charge more for "segregated" deliveries. They serve kind of as a commodity exchange and fuel logistics where oil companies put in commodity grade fuel and the pipeline operators figure out how to get the same commodity grade to the oil companies' customers. Their incentive is to transport fuel the shortest distance possible. So if an oil company's customer is 1000 miles away, there's a pretty good chance that the base fuel came from a refinery much closer to the end customer. And this stuff is often blended together in storage tanks, where it could come from several different refineries making the same commodity grade.