Originally Posted By: Boomer
Almost all gasoline in a given area comes from the same tank farm/supply line. As such there is NO difference in the base fuel. Additives do differ and they are added as a truck fills up. If the fuel is Top Tier (see their Web site), you are gettin a higher level of additives than required. Since the fuel is the same in an area,and only the additives differ, I always find these anecdotal stries of wild mileage changes to be on the side of urban legend.
I have kept very careful track of mileage in my cars and trucks and really don't see this. I do see a difference in my Nissan VQ 40 engine depending on octane grades as it is set up for running on 91+ octane fuel. It may be that some styations are having a lower octane fuel put into their super tanks but that is illegal.
I don't agree on your urban legend. I've never noticed any difference between a top tier such as Shell and just a name brand like Mobil or something. I remember watching something on Discovery maybe about how the fuel system works.
The fuel company deposits whatever grade fuel it may be (say 91 for instance) into the pipeline. They run through the pipelines and each unit is sepperated by soemthing thing called a "pig" that seems like a big plunger or sealed devider.
So Company "A" deposits 100 units for instance, and Company "B" deposits 100 units, and so on. Well, at the other end, company A will withdraw 100 units from the system, though it would not be the same 100 units that they deposited. But it does not matter, because at that point company "A" takes it's units, adds it's additive packs, and cleaners, or whatever their formula is into the fuel and then ships it out to the stations. So Mobil's end product would differ from Shell, and Marathon, or whatever company is shipping it to their stations. I'm sure at that point, one company prob has a higher quality additive package than another one.
Anyway, back to the original urban legend. My experience is totally unbiased, but I can tell you that I drive m-f ~30miles each way on the same roads, at the same time, with similar traffic. Again, I may make a run here or there to the store or something. But at least in my car, I consistently get aprox 380-400ish miles to a tank when I'm using corner station "house hold names". And I consistently get about 340-350ish out of my tank when I fill up at the Costco by my house. So to me there is something different. It may not effect everyone the same way, but for a fact which I have duplicated over and over, I just don't get the same distance out of the Costco fuel. As far as I knew, say here in Michigan, the fuel can't contain more than 10% Ethanol unless it is E85 or something. I don't see how some companies could double up, or add more ethanol and get away with it with with all the certification stickers I see all over the pumps that get updated.
Either way, to save 5-10 cents a gallon at Costco just means that I have to fill up a day or so earlier than I do when I'm using other stations gas.
I supposed that is not totally scientific, but it also is not just me being so in love with a certain brand product that I try to always look and promote how much better it is, as some people like to do with their expensive oils and whatnot.