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Gas Pumping Secrets From a Physics Whiz

I hung out with a fluid engineer who works for Chevron in San Ramon, CA. His job is to design oil pipelines that safely transport oil using the least amount of energy and money.

This dude is a total physics master, and he knows everything you could possibly know about pumping gas. He told me some gas pumping secrets that I could share with you guys.

1) Don’t Hold the Trigger of the Gas Pump Handle All The Way Down
The trigger on the gas pumping gun has different speeds depending on how far you press down: slow, medium, and high. If you hold the trigger lightly, gas will pump more slowly. However, this is important because slow moving liquid produces less fuel vapor. All gas pump systems have a “vapor return system” that carries gas fumes back to the gas station’s underground storage tank. Those vapors are lost $$. Pumping at full speed generates a lot of vapors that end up getting sucked back.

2) Pump Your Gas When It’s Cold
Gas stations store their fuel in underground storage tanks. Heat causes all substances, including gasoline, to expand ever so slightly. So if your gas on a really hot summer afternoon, you are getting slightly less than you would if you pumped gas on a cold morning.

3) Don’t Fill Up When the Gas Truck Is Delivering Gas to the Station
When the gas tanker is delivering gas, the fuel in the underground storage tanks is sloshing around. Dirt and other sediments that usually settle at the bottom of the storage tanks may get mixed into the fuel that ends up in your gas tank.

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Comments (31)
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31 Existing Comments
  1. Website Design said:
    on July 20th at 12:28 am

    wow, interesting tips. I was filling up today and noticed the gas station doing a promo for 3 cents off a gallon if you use a debit card + pin. Although it doesn’t beat the amex it is a great idea!

  2. Steve said:
    on July 20th at 01:15 am

    Yes, thermal expansion will have some impact, but it will be minimal. The gas is in an underground storage tank where the temperature is generally constant, but the time to dispense will not heat the gas up enough to make this a significant issue. I am surprised that you “engineer” didn’t mention the temperature of the gas while the gas truck is refilling. Gas in a gas truck will be hotter than gas in the underground tank. It will take time (a day or so) to reach equilibrium at the cooler temperature.

  3. Steve said:
    on July 20th at 11:08 pm

    My dad owned a service station and died of lung cancer. Stay away from fumes!

  4. Drew said:
    on July 20th at 11:55 pm

    Those tips may be valid, but are probably very insignificant. HOWEVER, I think it would be beneficial for people to NOT drive with full gas tanks. Try to keep your tanks at 1/2 full or lower all the time. This will reduce the WEIGHT that your car has to lug around!!

  5. jason said:
    on July 21st at 10:00 am

    these tips are garbage.

  6. T said:
    on July 21st at 01:18 pm

    Yea, these tips are garbage. Only valid one is maybe the last tip, but who the heck wants to wait to make sure the sediments settle down? Also, does this so-called physics master know how the flowmeter operates at gas station? Typically, the margin of error on a flowmeter will work both ways (plus-minus). So over the long run, you might even be getting more gas than losing gas by squeezing the handle down. Oh, and you save time by not looking like a dolt too. Imagine that.

  7. WhySoSerious said:
    on July 21st at 07:21 pm


  8. Joe said:
    on July 23rd at 03:35 pm

    I was tring to fill my gas tank at a very slow speed to save fume but It took more than 5 minute to fill 5 gallion. I don’t think its worth my time to save few pennies.

  9. J. Wu said:
    on July 23rd at 04:19 pm


  10. scott said:
    on July 23rd at 05:52 pm

    Sure is quiet out there. . . What’s about to happen? ? ?

  11. tom b said:
    on July 23rd at 07:01 pm

    In Canada, the gas pumps have a device to compensate for temperature variation, so that people don’t get more gas or less gas than they should. Believe it or not, gas stations in the USA do NOT have this, and apparently the powers at be are fighting to keep it that way.

  12. Larry said:
    on July 24th at 12:16 am

    I wish I had moved to Canada 40 years ago-I wouldn’t have had to serve in the Army and I’d have saved a lot on gas. Gas stations all across America recalibrate their pumps to cheat their fellow Americans.

  13. tom b said:
    on July 24th at 02:40 am

    I was in Canada last year however, and the gas cost significantly more than back here. But at least they get exactly what they’re paying for.

  14. tom b said:
    on July 24th at 02:42 am

    also, that higher price may have had something to do with the fact that the dollar is extremely weak and doesn’t buy anywhere near as much as it used to in other countries.

  15. J said:
    on July 24th at 05:53 am


  16. bob bob said:
    on July 30th at 07:24 am

    best way to save gas—stay at home more–you do not have to go somewhere every day just to be going

  17. Arkie said:
    on July 31st at 06:15 pm

    What does “I love lamp” have to do with gasoline pumping?

  18. JustAMan said:
    on July 31st at 07:02 pm

    The prices are higher in Canada because the have a more socialistic system. Even when the dollar is strong it cost much more in Canada to fill up.

  19. tom b said:
    on August 1st at 04:46 am

    Yeah, the prices are higher in Canada. Last time I was there a tobacco shop was charging $3 for my favorite blunts wraps. Just for one!!! Back here in America I the same ones for $1.25. Those socialist bastards and they’re taxes. Sure, maybe those taxes will be helping some poor schlob with cancer to get treatment, but $3 for a blunt wrap??? Gimme a break!

  20. Dan Tanner said:
    on August 2nd at 10:57 pm

    Why dont some people file Anti-trust suits against Oil companies and stop this all gang bang price gouging? Have you seen the mega Earnings of these Oil companies this quarter ? It will shock you.

    (These tips are like trying to squeeze the last sliver out of your toothpaste).

  21. Kevin said:
    on August 3rd at 03:59 am

    Exxon had a profit of just under 12 Billion last quarter ( a wopping 6% return on revenue) this after the government took its cut of over 30 billion, who’s the rip off artist.

    (These tips don’t matter, I’m losing 4 MPG to the 10% ethonal mix).

  22. Aaron said:
    on August 5th at 07:59 pm

    Exxon Mobil, which on Thursday reported the highest quarterly profit ever and is the main target of any “windfall” tax surcharge. Yet if its profits are at record highs, its tax bills are already at record highs too. Between 2003 and 2007, Exxon paid $64.7 billion in U.S. taxes, exceeding its after-tax U.S. earnings by more than $19 billion.


  23. tom b said:
    on August 7th at 07:29 pm

    aaron you are completely right. those poor big oil execs. they suffer sooo much, we should really just let them make as much as they want without getting mad; we wouldn’t want to hurt their feelings.

  24. John D said:
    on August 8th at 12:54 pm

    Tom B, the oil execs are not getting any of those profits – their salary comes from earnings, not profits. If you are invested in any mutual funds or have 401k investments, you are probably getting some of those profits. The dollar amounts may be large, but the profits as a percentage of earnings is not as large as many other corporations in the US. If you want to impose a windfall profits tax on Exxon Mobil, then they will either locate to another country or go out of business. Either way, many US jobs will be lost and billions of dollars they pay in taxes will not be going to the US Treasury. Making a 6% profit is not evil!

  25. tom b said:
    on August 9th at 01:04 am

    wow they even pay oil reps to prowl the bankaholic forums.

  26. George B said:
    on August 9th at 01:08 pm

    Actually, all of you are incorrect.

    The price of oil is determined by the Stock Market. I know…I trade oil daily. Oil goes up and down based upon the “perceived” worldwide supply and demand.

    Why has oil price gone up so quickly? Because of the American voter. 30+ years ago, the Middle East held the world hostage by withholding oil. That, along with increased world demand, creates an undersupply relative to demand. Supply is lacking because the world, especially the U.S. has not done anything about that crisis. There have been very few, if any, advancements in fuels. We even stopped drilling for oil, building refineries, and stopped building nuclear plants. Now, one can argue the reasons for these to occur, but it comes down to the (at least for the U.S.) American public allowing our leaders to not have an energy policy.

    Yes, oil companies will pay billions in taxes this year, but guess where that comes from – the American consumer. It’s another way for the government to get additional revenues without raising taxes (officially).

    Some say that we should get used to high gas prices because the UK pays even more than us. That’s because the UK doesn’t have all the other taxes we have here in the U.S. and that shortfall is made through their gasoline prices.

    Energy is the lifeblood of a country. And when it is relatively more expensive (percentile of commodities), everything else will eventually soar in price.

    It’s a numbers and money game and the only way to beat it is for us voters to voice our opinions. Or, do as I do…invest some, and it doesn’t take much, money in oil – that’s what the airlines do to hedge rising oil prices.

  27. sid frends said:
    on August 24th at 01:53 am

    I get free gas every time I eat at Denny’s

  28. Ann said:
    on August 30th at 01:16 am

    I read some of the comments and had to stick my two cents in. It is true about the tanks being filled and the sludge getting stirred up. I was also told my a mechanic to keep your gas tank half full or more. This is true for older cars, sludge sits at the bottom of your tank also (I have 200,000 mile on my 1993 Jeep). I think something was lost in the transfer of info. When you pump gas fast air mixes in with the gas and you can get less gas for your money, so squeeze slow and steady. Pump your gas during the coldest part of the day, the fumes are not good for you or the environment (save the planet and all that). Thanks for reading my thoughts…

  29. Love said:
    on September 23rd at 03:47 am

    Ann, just how you said it is just how I interpreted it. All are good tips to keep in mind and use as we see fit – I will definitely be implementing them in my daily life.

  30. Mike Mancil said:
    on September 25th at 01:07 am

    Hydrogen mixed in gasoline gives it more power. Imagine more power from FUEL! With more power you don’t have to use as much to get moving. Simplest method. The oil companys know this, but don’t like it. Because it is Simple-Cheap-Clean and as safe as any other gasoline type fuel, and not as profitable to make ……………..
    Disturbing american antics.

  31. Andrew said:
    on October 7th at 10:39 am

    ‘Pump your gas during the coldest part of the day, the fumes are not good for you or the environment (save the planet and all that)’… +100. Saving the planet (and all that…) is important and a concern of mine! Unfortunately, here in South Africa, we have staff whom man the pumps. People need jobs! I’d happily do my own and implement all measures mentioned. If I did, I’d probably be removed from the premises! Lol.