Gas Stations; Stale gas?

[spacemanspif]

I'll be the first to admit that I don't do much "hard core" experimenting with my ecomodding mostly because I have no instrumentation and all my results are tank to tank. But something has me thinking and it involves the gas we burn and the brand it's sold under.

In my town I have a Wawa (convenience store with gas station) and Sunoco at easy disposal to purchase gas. There is also a Valero. Since I started driving I've bought the cheap gas and my hot rod type friends have always said to buy good gas not cheap Wawa stuff. Well one day I saw that the price at Sunoco was the same as Wawa so in the back of my mind I heard my friends and decided I'd start filling at Sunoco since it's "better" gas (according to popular opinion of friends).

Every now and then I still fill at Wawa though when it's more convenient or I'm out elsewhere and Wawa is still cheaper. For reference during morning and evening rush Wawa has every pump running and every other station has maybe 3 people filling on 6-8 pumps. In tracking my fills over the last 3 weeks I see that my last tank (Sunoco) was 40mpg, the previous tank was Wawa and an all time high of 47mpg, and the tank before that was 41mpg on Sunoco gas again. My current tank still has many miles to empty but is Wawa gas again and looking better my usual 40mpg tanks.

I know this is hardly scientific but could I be getting stale gas from the "better" gas station causing lower MPG performance? Thus, could it be better to not shop for gas by brand but rather by how busy the station is?

Side note, Sunoco and Valero are not listed on the list of top tier gas stations, does that mean it's definitely not better than the "cheap" stuff? Top Tier Gasoline

All I know is that if I get better than 43mpg this tank, I believe that I'm better off with "cheap" gas than the name brand stuff...

Thoughts? And sorry if this has been beaten to death, I searched a little but may have overlooked it.

[redpoint5]

I'm not familiar with those brands, but gas is gas, unless it has extra detergents. and even then it's still just gas. There are way too many variables at play to attribute better mileage to the brand of gas you happen to be running.

In fact, I sometimes run 87 octane fuel from Arco in my TSX, and sometimes I run 92 octane from Costco (Top Tier), and I can find no pattern of one having better fuel economy over the other. My car is even tuned to run best on 91 octane, so you would at least expect it to get better fuel economy on premium.

Stale gas isn't an issue unless it's sitting for months, and then the biggest concern is water absorption.

[backpacker3]

I was always taught to avoid buying gas at places that aren't busy because they might be selling gas that could be over a month old because they don't have enough business to need to fill the tanks sooner and not to get gas right after they have filled the tanks at the station because it stirs up sediment and crap at the bottom of the tanks at the station that can then mess up your car.

I don't know how true either of those are but logically they make sense so I usually try to follow them. I do know however that if you have gas sitting in your car for 3 months that you'll start having problems at that point.

[Daox]

I've never really seen any significant difference from different brand gas either.

[user removed]

Is it possible that filling at one station does not get your tank as full as filling at the other station?

Notice any difference in the way your car runs?

From personal experience, I have seen gas in cars (ethanol blends) that was fine after a year, but that is mostly due to vapor recovery systems. Leave the gas cap off and you would have real problems with the same gas.

Underground storage tanks generally do not see any significant difference in temperature regardless of ambient variations and they are fairly well sealed from the environment.

I buy the cheapest gas I can find, last two tanks were Wal Mart at $3.289. Plenty of traffic there since they usually beat the other local stations with the 15 cent a gallon discount, although I have bought gas out in Gloucester county for the same price from a Shell station.

regards
Mech

[backpacker3]

I have noticed certain gas stations that consistently give me lower gas mileage. So I avoid those.

[rbrowning]

A few years back I was commuting a crazy distance that burned a tank of gas every other day. At the time Speedway brand was offering a $.05 per gallon discount if you had their loyality card so I frequented them. When the promo was over I got curious and decided to compare them to BP across the road. I ran each brand in alternate tanks to help offset environmental influences as much as possible. After 10 tanks of each I found that BP had averaged just under 1MPG better. But that was in a Chevy Silverado getting about 18MPG, YMMV.

[XYZ]

Originally Posted by backpacker3

I was always taught to avoid buying gas at places that aren't busy because they might be selling gas that could be over a month old because they don't have enough business to need to fill the tanks sooner and not to get gas right after they have filled the tanks at the station because it stirs up sediment and crap at the bottom of the tanks at the station that can then mess up your car.

The first idea is a myth. Gas stored for a month in a sealed tank is not a problem.

The second idea used to be plausible decades ago. In more modern times pumps have filtration systems on them.

I don't know how true either of those are but logically they make sense so I usually try to follow them. I do know however that if you have gas sitting in your car for 3 months that you'll start having problems at that point.

No, that's not true either. I have a car that is in storage for more than six months per year and have been doing that for decades. Never had any problem with gas left in it.

[XYZ]

Originally Posted by redpoint5

I'm not familiar with those brands, but gas is gas, unless it has extra detergents. and even then it's still just gas. There are way too many variables at play to attribute better mileage to the brand of gas you happen to be running.

Very true. Might as well buy gas where it is cheapest. When you buy from an unbranded station, the gas your are buying is usually surplus gas from a branded shipment. You won't know what brand it is, but it doesn't matter.

The only time I ever noticed a difference in mileage was decades ago when Shell was advertising it's superiority with inclusion of an additive called "platformate".

Oil and Petroleum Commercials: Super Shell

I was on a cross country trip in the 1970's in an old American car that was carbureted. The best price of gas in one town was the same as that for Shell brand, which I had never used before because it was always higher priced. We filled up with Shell and at the next fill-up we found that our MPG was significantly better than using the usual no-name or non-Shell gas. I and my traveling companion are very skeptical by nature, but we had to admit there was no other explanation other than that Shell gas apparently had different additives in it. I never used Shell after that because their higher price offset any advantage in mileage gained. But as reluctant as I was to admit it, there must have been some truth to their advertising, because that one tankful of gas did produce superior results.

[TexasCotton]

Originally Posted by Daox

I've never really seen any significant difference from different brand gas either.

I am going to second this and survey says the following
Most gasoline,diesel, and blended fuels are truck tanker fuel delivered in my local area. The tankers are contracted by the retailer and some of them may place branded logos on them. Shell and Chevron where the last hold outs in the non contracted fuel delivery(kinda depends on where u live in relation to the tank farm terminal). My understanding the better quality gasoline (last refined) and best nationwide price would be Tulsa Oklahoma .My understanding the refinery, pipeline, and tank farm terminal distribution point are basically next to each to other in that city