(photo by Seetwist)

Being that I am a big advocate of riding a bike to save gas, every now and then in our lovely suburbanized America, we can’t avoid using a car. (News flash: those of you think you’re saving the environment by driving a hybrid: you’re not.) Today, I got this email from my grandfather’s buddy in the oil and gas industry. Not sure if this is a spammy email forward making the rounds, or if he really actually knows this dude, but it sounds good.

Behold, a geek’s guide to saving gas (other than driving less!):

1. Fill up your car or truck in the morning when the temperature is still cool. Remember that all service stations have their storage tanks buried below ground; and the colder the ground, the denser the gasoline. When it gets warmer gasoline expands, so if you’re filling up in the afternoon or in the evening, what should be a gallon is not exactly a gallon. In the petroleum business, the specific gravity and temperature of the fuel (gasoline, diesel, jet fuel, ethanol and other petroleum products) are significant. Every truckload that we load is temperature-compensated so that the indicated gallon age is actually the amount pumped.

A one-degree rise in temperature is a big deal for businesses, but service stations don’t have temperature compensation at their pumps.


2. If a tanker truck is filling the station’s tank at the time you want to buy gas, do not fill up; most likely dirt and sludge in the tank is being stirred up when gas is being delivered, and you might be transferring that dirt from the bottom of their tank into your car’s tank.

3. Fill up when your gas tank is half-full (or half-empty), because the more gas you have in your tank the less air there is and gasoline
evaporates rapidly, especially when it’s warm. (Gasoline storage tanks have an in ternal floating ‘roof’ membrane to act as a barrier between the gas and the atmosphere, thereby minimizing evaporation.)

4. If you look at the trigger you’ll see that it has three delivery settings: slow, medium and high. When you’re filling up do not squeeze
the trigger of the nozzle to the high setting. You should be pumping at the slow setting, thereby minimizing vapors created while you are pumping.

Hoses at the pump are corrugated; the corrugations act as a return path for vapor recovery from gas that already has been metered. If you are pumping at the high setting, the agitated gasoline contains more vapor, which is being sucked back into the underground tank, so you’re getting less gas for your money.

5. Do not top off your gas tank, when the pump shuts off, do not keep trying to add more gas………………a friend who owns a gas station says that by doing this, you are actually giving the next customer a $1.00 worth of gas. The gas you pump stays in the hose and never makes it to your tank………..good to know.


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  • Wow, never knew that temperature affected gas that much. Interesting.
  • Great article. I agree about the "image of a hybrid" not really helping the environment, but it's a start. Shoot, the biggest polluters of CO2 emissions are humans....when we breathe. Dang, now that creates a quagmire doesn't it? I personally am lucky, because my small town in Oregon has free buses, which I take to "commute" to work. I guess we all have to decide to live/work in a better situation than drive all over the place.
    Cheers.
  • To save gas, I like to pretend I'm a hypermiler...not using breaks, coasting, etc.
  • Well, okay, I was just slightly skeptical of this email (as I am with all the forwards my grandfather sends... he's sent some wacked Fwds in the past). But I do feel like I read something about this in WIRED or something, that gas mileage goes way down during the summer months because of more rapid evaporation in gas tanks.

    @blackmailismylife: True, critical mass bike rides won't save the earth, either. But I do get a little annoyed by the self-righteousness people tend to get with they buy a brand new hybrid and act like they're "doing their part." That's bullshit and we all know it. Buying a brand new car, made of thousands of brand new materials shipped from all corners of the globe, to a factory in Asia, then shipped complete on big tanker ships to the United States is far less saving the world than, say, driving your old beater '85 Honda Civic until the thing dies.

    But all those arguments will be moot soon anyways, what with gas prices pushing $100/barrel and China lifting it's cap on subsidized fuel. Ain't gonna be no gas nohow.
  • Yeah it's spammy. Also, I think that it's fair to say that hybrids are improving the situation, since as you note, suburbanized America requires a ton of car travel, so whatever consumers might do to affectively upgrade CAFE standards helps. Sure it's a Reaganite mode of voting with one's wallet, but it's not like Critical Mass protests are doing much more than pissing people off.
  • About the topping off thing... Just push the metal flap inside the pump where the nozzle hangs. It'll shut off the meter, but allow you to drain the remaining fuel out of the pump hose.

    Temperature is probably not significantly important, because the underground fuel tanks maintain their temperature through geothermals. Tanks are usually sitting a couple feet underground, beneath 6" of concrete, surrounded by earth with a constant core temperature. Heat rises and fuel is pumped from the bottom of the tank, thus rendering this argument all but null from where I'm looking.

    As for fulling up when the tank is half full. I'd call bullshit on this one too, for a couple of reasons. The first reason is that one gets better fuel economy when there's less weight in the car. By not letting the car get down towards empty, one is missing out on the opportunity for maximum fuel economy. Secondly, filling up with gas takes time, and time is money (to some people). Therefore, the less time wasted at the pump, the better. I will admit, however, that neither of these things really makes any difference in the long run. But then again, nore do any of these gas saving tips.

    No offense, but I don't take car advice from a bicyclist ;)
  • Oh I got so screwed for not knowing these rules. I just spent over a $1200 for new fuel injector etc. for running the tank to fumes. Thanks Mark! Twitter Networking!
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