I just discovered something along these lines. I always put 87 in... just never thought about anything else. I've regularly been getting about 30-31 mpg. Then a few weeks ago, I had a tank that got only 26, and I was like WTF???... but the next one pulled 30 again. A couple of tanks later it happeded again. I started paying close attention to it, figuring that one of the stations had bad gas. In addition to keeping tabs of my mileage, I started righting down the station name/location on each fill.

It turns out that anytime I fill with Sunoco, I get from 29 - 31... if I fill with anything else, I get 24 - 26.

So with the added gas mileage, I figured out it's still better to buy at Sunoco, even if it were a full 10 cents higher/gallon.

BTW... my comute is 55 miles one way, mostly freeway. I average from 75 - 85 mph... which is probably why my mileage is really good. I took my car into NYC one day and came back with 23...

 

damn some of u guys commute real far !

I live 3 miles from school!

heard about stuff like cheap gas places have suckier gas and gas mileage... guess u helped us all clear out the rumor....

here in CA... ppl say ARCO is the worst.

 

Well.... I have to assume that each companies gas has a slightly different formula, otherwise there wouldn't be much competition. I mean, you see 3 gas stations on one corner by my house, and they're always priced within 1 cent (usually .1 cent).

I'm not necessarily saying that Sunoco is the best. I talked to my father about it... I remembered when I was a kid he had a pick-up that he would only put Chevron in. He told me it really depends more on what you break the thing in with. I guess that kind of makes sense. I guess you should use different gasoline like you're supposed to not drive the same speed consistently.

Anyway, I looked back through my receipts, and sure enough my first 4 tanks were from Sunoco.

 

sorry to burst the bubble of those of you who believe gas at one location (ie. BP or BP Amoco) is better than another (ie. Citgo)-but its not.

I used to work for a major gasoline (or petrol) retail chain and can tell you that its all marketing and hype. The method they use is so (except Canada. This only applies to the U.S.) secretive that it is protected by U.S. anti-trust law.

This secret is this: All gasoline tat you buy is the SAME! For instance, in Atlanta there are only TWO depots or distributors. One is the BP depot, which is the smaller of the two and is located in either Lawrenceville or Norcross (I cant remember offhand which). The other is in Powder Springs and is owned by Asheland Petroleum Co. LLC.
Both places are the only gasoline distribution depots in the South East and supply the northeast and central U.S. as well. This is why gas is almost always cheaper in Atlanta than everywhere else.

The only difference between the various gas station brands is the detergent amounts used in each. Dyes also may differ as well. If gas is bought from a BP depot it will be clear however as it is sold under the Amoco fuels moniker.

Every company's gasoline must be unique in order to claim that theirs has some sort of specialness about it. otherwise its false advertising and would violate anti-trust law. Thats why gasoline at one location may appear a slightly different colour than another. These dyes and detergents will NOT hurt your engine at all. they arent corrosive or the such and do NOT lower the octane points at all.

however, gas can lose its octane if its sits for very long. in fact, it can lose enough to cause knock when it says 89 octane on it. Some places are even known to put water in their tanks. Although this is usually done by the smaller and "no-name" gas stations, it is still uncommon.

Believe it or not, when I asked the tanker drivers what could cause shitty gas they almost always said it was due to either the tanker driver messing up and putting the wrong octane in the wrong tank, or they were told to do so at the order of the station owner.

Lastly, in order to raise octane levels to like 93 and 94, an additive is added to the gasoline like MTBE. These are called oxygenated fuels. Some states have banned their use and so they get only 91 as their highest. Even this is done at the "depots". I used to love it when I'd hear someone say that they'd never buy fuel at my station and that they only used Amoco. I never said anything but, it sure was funny when I'd see our receiving slip and it said, "BP Depot". Believe what you will, just use a busy station to get good gas.

 

In Canada it is the same thing. I used to work for an oil company (Husky Energy, brethren of Exxon Mobil) and we always laugh at people who talk about boycotting a brand of gas station because they are directly linked with the refinery of the same name. This just ain't true, these guys get their gas from the local distributors, which may or may not be their parent company.