Are You Getting Ripped Off At The Gas Pump?

A few weeks ago, my Aunt sent along an email that warned about mis-calibrated gas pumps. The email was adamant that pumps were overcharging for gasoline because the total amount didn’t really match up to the price times the number of gallons.

My Gasoline Ripoff Non-Scientific Test.

Two weeks ago, I took a car trip across the width of Kansas on I70 and into Colorado (to Denver). Since this warning was fresh in my mind, I decided to test it. As I sailed across the prairie, stopping at station after station, I kept my receipts and tracked the price per gallon and gallons purchased. Since I was alone, I didn’t linger to figure out the total after pumping the gas, but just stuffed the receipt in my purse for a later calculation.

I pay pre-pay with cash and so request a dollar amount instead of a specific number of gallons. Then I set the pump handle and let the pump decide when to quit.

Here were my results:

Price Per Gal # Gallons Total Price Actual Price Difference
$3.65 8.221 $30.00 $30.00 -$0.001571
$3.69 6.759 $24.94 $25.00 -$0.059290
$3.60 4.168 $15.00 $15.00 $0.000632
$3.66 4.099 $15.00 $15.00 -$0.001759
$4.02 2.482 $9.98 $10.00 -$0.022360
$3.79 7.897 $29.93 $30.00 -$0.070370
$3.79 5.264 $19.95 $20.00 -$0.049440
Total 38.89 $144.80 $145.00 -$0.204158

Was I ripped off at the gas pump?

Well, if you call paying 20 cents more on total purchases of almost $145 dollars being ripped off, then yes.  But I don’t.  This is probably within some legal margin of error.

Aren’t there regulations governing how this stuff works?

Yes, but the states are in control of inspecting the gas stations and pumps to make sure they are in compliance.

According to CBS News there is wide variance in how the pumps are inspected and how often it happens. Apparently some states have a shortage of pump inspectors.

Even if the pumps are inspected and do pass the inspection, you may still not get exactly what you paid for (as happened to me). There is a margin of allowable error in the calibrations, according to law.

CBS reported that: “So a high-volume station that routinely sells a little less than a gallon could rake in around $50,000 a year extra – for gas you never get.”

So, how can you avoid being ripped off at the gas pump?

Check Your Total

When you get gas, make sure that the price per gallon times the number of gallons is very close to the total charged.

If it isn’t, you can try talking to the gas station clerk or manager. You can also complain to the state agency responsible for inspecting the pumps to make sure they are correctly calibrated. In a lot of states, this is the weights and measures department.

You can also vote with your feet (or in this case your car tires) and go somewhere else.

Fill Up On a Cool Day

If you fill up on a hot day, you may get less than you paid for. According to Consumer Watchdog, that is because gasoline expands when hot, yet the pumps (most of which do not take temperature into consideration) do not change the amount of gasoline pumped, so you get expanded gasoline in your tank, which gives you fewer miles to the gallon.

Watch For Higher Price Per Gallon If You Pay With Credit

Some stations charge more for using credit than if you pay with cash.

Beware of Misleading Advertising

In Kansas and in Colorado, I encountered stations that advertised with big interstate signs that unleaded was a certain price. When I pulled into the pump, I found that the advertised price was for 85 octane gas, not the 87 that I usually get for the ‘unleaded’ price in my home state.

Use The Internet to Find the Lowest Prices in the Area

If you have the luxury of surfing to find the low price, our wonderful internet can help you find the best price in your area.

Here are a few sites that can help:

Gas Buddy


Gas Price Watch

What tips do you have to avoid being ripped off at the gas pump?


Are You Getting Ripped Off At The Gas Pump? — 28 Comments

  1. yes, according to your calculation there is a small difference, there is no doubt. But as you said it can be due to some decimals. But until it is only 0,20$ out of $145, it’s ok.
    But it is a great advice to check always if you get for what you paid. From now on I’ll check it.

      • It’s funny that you mention that. Every single car that my dad has owned a book in it where you get track of when he filled up, how much it cost, the price per gallon, and the total number gallons. Thesis it down at the end of the month and go through each and every entry to calculate the miles per gallon for each of the vehicles. It seems excessive but he was very frugal and wanted to know where his money was going. If you noticed the discrepancy with one of the gas stations used, he would make note of it and never go there again.

  2. I never knew this was a problem. I will have to math check my receipts. It is worth noting most gas stations add nine tenths of a cent to the per gallon price.

    I have heard about the gas expansion when hot and now try to get my gas on my way to work instead of on the way home. I doubt it makes much difference but when I stop to get gas doesn’t matter to me.

  3. At least you’re not being taken advantage of “volumetric calibration” which is leagal in Canada and ILLEGAL in the USA.

    Pumps here are calibrated for “15 degrees C” which means that when it’s less than that we get ripped off.

    Since gas is stored in the ground and the ground temps seldom climb higher than 5-7 degrees here we get ripped off 98% of the time.

    The colder it gets, the more we get jacked.

  4. Thanks for the post Marie. There’s a lot of uncertainty in the world today and with gas prices continuing to rise it becomes more and more important to make sure that you’re not being ripped off. I live on the East Coast and there was a gas station in New Jersey that would adjust their system so that the pumps were charge for a gallon or two more there was actually pumped. They did it so randomly, that it was very hard to track and when the inspectors came to check things out, somehow the adjustments were reverted so that the pumps operated correctly when inspected. Once the inspectors left, they made the changes again. There a lot of scammers out the world and everyone needs to be cautious.

  5. Fantastic tips, Marie! I’ve never thought to compare the cost on the pump to what I’ve gotten…how naive is that? It’s also amazing to me that filling up on a cool day would beat a warm one. I wonder how much money that saves?

  6. I have wondered about this before too! It may not seem like a lot, but if they get a few cents from all of their customers it all adds up!

  7. I love Gas Buddy! I only recently started using it, but now I never get gas without it. It’s crazy how much the prices can change when you go a mile down the road. I never thought to check to make sure that the price matched up with what I actually get- it’s something I guess I take for granted! Your study is reassuring though. Thanks!

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