Help me with my gas problem.

September 5, 2005 9:16 AM

GasFilter: How do I learn more about the quality of various gasoline brands? Also, how can I determine who supplies gasoline to a particular retailer? For example, is Speedway gasoline really the same as Sunoco gasoline (since Sunoco purchased them), or do they still use their own gas? How about the gas at my local Sam's club, or Jewel-Osco -- who supplies that gas to them?
posted by Merdryn to travel & transportation (11 comments total)

As I understand it, it's not so much which refinery the gas comes from that determines the "quality", but the additives used and the condition of the station's holding tanks.
posted by trevyn at 9:39 AM on September 5, 2005

It's all the same gas. The only difference is additives, the soapy mixtures that clean the engine. These are in such small percentage that I doubt there's any real difference between one additive and another. The government mandates the lowest possible additive concentration, but you're allowed to go over this. Some companies, in order to claim that their gas is "better" will double the additives. The gas is the same, though.

People who own gas stations either 1) have their own trucks, 2) contract with a particular trucking company, or 3) use several different trucking companies.

When they ask this company to resupply one of their stations, that trucking company dispatches a driver to one of the terminals in the area (a tank farm with several million gallons on-site where tanker trucks load) where they have an allocation of product. This allocation is virtual, it is just a number representing a portion of the liquid stored in one of the large tanks on-site. Terminals are supplied by pipelines (like Colonial or Plantation on the eastern seaboard) or by barges, like in Chesapeake, VA.

So, say the regional manager of the BP station is running low at one of his stores; he will contact the trucking company and ask for a delivery to be made. That trucker will ask "which terminal?", the regional manager will pick based on price, and, in the case of BP, will pull from BP's inventory at that terminal. For smaller companies that don't have their own inventory at terminals, the trucking company pulls from the inventory of a large supplier, like BP, Amoco, Chevron, and the small company pays this large company back. When the truck driver gets the call, he drives to the terminal and swipes his card. The terminal computer checks to make sure that this driver for this trucking company has authorization to pull out of BP's inventory. If it does, they proceed through the gate, hook up their truck, and start loading. As the fuel is flowing into the truck, additives are injected. This is either a generic additive, or special BP additive (which may just be twice as much generic additive). When the next truck gets in line, he does the exact same thing, and gets the exact same gas. He might be pulling it from the exact same tank, but be paying a higher or lower price depending on the company he's been instructed to buy from.

Again, there are only two kinds of gas. Premium and Regular. Midgrade is a mixture of the two. That's all there is at the terminal. The additive mixture gets put in as its loaded into a tanker truck.
posted by odinsdream at 9:46 AM on September 5, 2005

odinstream has put it very well. There is only one other thing I'd like to add, which is that quality is marginally affected by the amount of water and other contaminants in the gas, which is in turn affected by the filtration. Each pump has filters which need to be changed regularly, and often are not, and the tank as a whole I believe has a filter as well. I don't think this follows brand lines so much as it does owners of particular stations. So I don't know how to tell where the good place to buy gas is. I try to buy from the same place provided the price and quality seem to be consistently OK.
posted by RustyBrooks at 10:19 AM on September 5, 2005

Excellent info; now, is there any evidence to support that my car (a model 2005 small SUV) would benefit from an aftermarket gasoline additive, assuming the gasoline itself complies to federal minimums for fuel additives?
posted by Merdryn at 10:37 AM on September 5, 2005

... assuming the gasoline itself complies to federal minimums for fuel additives?

If it doesn't, someone's supposed to be in quite a bit of trouble.

Cars that "knock" with regular gas can benefit from octane additives in the sense that you can stop the knocking.
posted by odinsdream at 11:04 AM on September 5, 2005

odinsdream: What about ethanol? In my experience, there are stations that have a mix of 90% petrol and 10% ethanol for every grade, some that are all petrol, or some that have a grade that's all petrol and a grade that's 90%/10% at the same pump -- and it says so on the pump. These stations are often across the street from one another with different mixes (although I've only seen the some-ethanol-mix grades/some-100%-petrol grades at the same pump at stations in the Midwest, where the Ethanol mix is cheaper even with higher octane). IMHO, a 10% ethanol mix can't really be considered that small of a percentage -- do they actually mix the ethanol at the pump, too? Is there a separate ethanol tank at those stations?
posted by eschatfische at 12:18 PM on September 5, 2005

Great answer odinsdream.

The only additive I've had recommended by anyone I trust is Techron. I put about $20 worth in a full tank approximately once a year because it makes me "feel" good. May not make a bit of difference. In fact, the person that recommended it put it more in terms of that he didn't think much of any of them but if one of them was going to make a difference it was probably Techron. This was coming from an experienced BMW mechanic.
posted by Carbolic at 12:24 PM on September 5, 2005

Changes in Gasoline III is a 40 page .pdf file that gives a pretty clear explanation of many factors affecting gasoline quality, and how they relate to automobile operation and driveability.
Long story short: "gasoline" is not necessarily a fungible commodity.

Gasoline is actually a blend of many fluids and gases, which are intentionally varied by refiners by geographic locale and season, to deliver generally good performance in most cars, for the atmospheric conditions likely to be encountered where the product is sold, and thus likely to be used. But the formulation of "gasoline" sold in the summer in San Diego will be significantly different than that sold in Boston in winter, since the Boston driver needs a fuel that is more volatile in order to provide better cold starting, while our friends in San Diego in the summer need protection from vapor lock which would probably be induced by the Boston winter mix, if it were inadvertently sold to them.

Also as odinsdream noted above, additive packages can vary significantly between retail products sold as "gasoline." There are federal standards for minimum detergent additive levels, and for mandated anti-smog additives such as MTBE, but some car manufacturers feel that these minimums may not be sufficient to ensure troublefree operation of their cars, and have established the Top Tier standard for detergent gasoline additives.

The success of formulations made by refineries is also influenced by the fuel distribution network. Generally, "gasoline" is not like wine, in that gas doesn't improve with age. So, it makes sense to buy gas from stations doing a reasonable volume. But buying at the biggest station in town does you little good if they are buying "spot market" gas from several distributors, based on price and availability alone. What you are looking for are stations that have plenty of traffic, to ensure frequent deliveries, but that don't constantly have a parade of delivery tankers. A station with modern tanks, sized correctly for its selling volume should be getting 2-3 deliveries a week, and that will ensure "fresh" gas with minimum fuel turbulence in the storage tank, which keeps dirt and water problems to a minimum as well.

It is also important to consider purely individual factors in choosing where to buy gas, such as the kind and age of the car you drive, its state of repair/tune, and your driving patterns. If you have an older American car with a V8 engine, which has a carbuerator instead of fuel injection, and it's not in good shape, and your average trip is 5 miles or less, you may be a lot more interested in gas with greater volatility, for good starting and short trip economy. But if you are driving a couple year old, fuel injected 4 cylinder "pocket rocket," 25 miles each way to work every day, detergent additives may be a lot more important.

Finally, with the recent damage to refineries in the New Orleans area, the Feds have (temporarily) relaxed regulations on anti-smog oxygenation additives like MTBE in some metropolitan areas, in order to improve the overall supply of gas in the coming weeks. So, I think there is going to be a lot more "trans-regional" shipping of gas from one area of the country to another, to meet spot shortages in coming weeks, than we'd usually see. And of course, this is happening as we change seasonal mixes from hot summer gas, to fall and winter formulations. So, I think there are going to be greater than usual complaints about gas quality across the country in coming weeks, and my personal opinion is that it may pay, even in these times of inflated prices, to stick with major brand outlets, some of whom have some sort of quality guarantee that will pay for engine damage that can be attributed to gasoline quality. Keep your reciepts!

And if you have any doubts about your car's state of repair, now would be a good time to replace air and fuel filters, and have a tune up and oil change, so that your vehicle is ready to make the best use of whatever it is you will be putting in its tank in the coming weeks...
posted by paulsc at 1:20 PM on September 5, 2005

eschatfische, ah ethanol. I forgot about that. Sorry! In my experience, which is limited, the ethanol is mixed in to the gasoline to control the vapor pressure. It's mixed in to the entire inventory in a single multi-thousand-gallon storage tank. As far as I know, this is a decision left to the terminal. I suppose in the cases where BP or some other large company owns and operates an entire terminal, they can make a decision about the mix of ethanol which would directly affect the gasoline quality only for customers of said terminal, but I don't know about this and can't speak to how it's handled. I did not consider ethanol as an additive in my answer above.
posted by odinsdream at 5:52 PM on September 5, 2005

most refineries I deal with actually blend 3 grades of gasoline. I haven't heard that mid-grade is just a mixture of premium and regular.

regarding the recent relaxation of enviro regs, I hear that this will allow us to import gasoline from Europe which currently has excess refining capacity but doesn't meet our "stringent" environmental standards.
posted by jacobsee at 11:13 AM on September 7, 2005

jacobsee; that's all midgrade is as far as I've dealt with it, which is in the southeast, from virginia to georgia.
posted by odinsdream at 7:17 AM on September 8, 2005