Chain mail education: Money-saving at the petrol stations

So, the petrol prices has been skyrocketing and you are finding your funds vaporising (pun-intended) from your bank account. Have a read of this e-mail that just dropped in this morning (validity up to reader’s discretion):

  1. Do not pump [a] full tank of petrol. Many of us are [un]aware that the petrol kiosk pump has a return pipe-line. When the petrol tank (in the car) reaches full level, there is a mechanism to trigger off the pump latch and at the same time a return-valve is opened (at the top of the pump station) to allow excess petrol to flow back into the pump. [Yet] the petrol has already pass[ed] through the meter, meaning you are donating the petrol back to [the station].
  2. 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 gallonage 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.
  3. 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.
  4. 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 internal floating ‘roof’ membrane to act as a barrier between the gas and the atmosphere, thereby minimi[s]ing evaporation).
  5. 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 minimi[s]ing 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.
  6. 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.

4 Comments so far

  1. neil on May 12th, 2008 @ 3:36 pm

    Haha. Those are ridiculous. Sounds like a case for the Mythbusters.

    Here’s my tip, Petrol is the lowest on Tuesday nights/Wednesday mornings. It goes up on Wednesday night/Thursday mornings. Simply fill up on Tuesdays.


  2. neil on May 12th, 2008 @ 3:38 pm
  3. Saving Gas « Spring City Chronicle (pingback) on May 13th, 2008 @ 8:46 am

    […] are some better ones from Australia (home of Mad Max and you know how much he liked his gasoline)  including: don’t fill up when […]


  4. Darren (darrenliz) on May 13th, 2008 @ 2:03 pm

    I agree – they do sound suspicious.

    Here’s one for rented cars: You never have to fill the car up ’til when the automatic latch goes off – all petrol tanks can be ‘over-filled’ beyond the ‘full’ mark. You can often save yourself a couple of dollars not waiting for the pump to cut off, and still have a ‘full’ reading on the indicator.



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