Topping Off: Learn Why You Should Never Top Off Your Gas Tank

gas tank full of money

It can be a hassle to head to the gas station to fill up every week or two. So when you’re standing at the pump, have you ever topped off your tank thinking it will save you time between trips? Or to round the price up to the nearest dollar?

If so, read below to learn the top five reasons why you shouldn’t top off your tank.

Why topping off your tank is a bad idea

According to the United States Environmental Protection Agency (EPA), topping off your tank is a waste of money and dangerous to you, your car, other people and even the environment. Find out why you should always skip this all-too-common practice.

  1. The gas can spill when overfilled. No one likes getting gasoline on their hands or clothes. It’s also problematic for a variety of other reasons:
    – It’s hazardous
    – It’s flammable
    – Spilled gasoline can seep into the ground, potentially polluting the water and harming wildlife
  2. The fumes are toxic. Gasoline vapors are harmful to breathe and toxic to the ozone layer. According to the EPA, evaporation and fumes from spillage contribute to the pollution problem by releasing toxic air pollutants such as benzene, which is not only toxic and flammable but carcinogenic.
  3. It’s a waste of money. Once you hear the first click of the gas pump, did you know any gas you pump after that isn’t going into your car’s tank? You’re actually paying for gas that is filling up the hose, ready to be pumped into the next customer’s car. Any additional gas you try to pump into your tank may be drawn into the vapor line and fed back into the station’s storage tanks.
  4. It can cause the gas pump to break. Most gas stations have a vapor recovery system. When you top off your gas tank, you can cause it to break or become inoperable. This problem can add to the air pollution problem and cause the gas pump to fail for the next person in line.
  5. It can ruin your car. Have you ever wondered why your vehicle won’t allow you to add more gas once you’ve been alerted that your tank is full? Because gasoline needs room to expand, your tank needs extra room for that expansion. If you try to top off, the extra gas you’re trying to add may actually evaporate into your vehicle’s vapor collection system. This can ruin the mechanism, making it work improperly, and cause your car to run less efficiently.

Once you understand the dangers of this common practice, hopefully you’ll think twice before ever topping off your gas tank again. Avoid the risks of personal injury, vehicle damage and environmental harm when you play it safe at the pump.

Another way to stay safe is to have auto insurance to keep you protected on the road. Many insurance companies also offer roadside assistance programs to give you the peace of mind, wherever you are.

22 Comments on "Topping Off: Learn Why You Should Never Top Off Your Gas Tank"

  1. Used Cars St Cloud

    What does topping off even mean? What I do is I put the gas pump in the tank and let it run automatically until it stops by itself. It just stops by itself when it is full. Is that considering “topping off”? I do this because I’m lazy and don’t feel like standing there waiting… Besides, how would I know if it almost full or not and when the right time to “stop” filling up? I don’t know so I let it run.

    • Chris Burdick

      After the pump automatically stops itself, many people will pull the handle a few more times to pump as much gas into the tank as possible. That’s topping off.

      It’s best to just stop when the pump stops itself.

  2. Jacqueline Colicci

    Thanks! I Googled this topic so my husband could see why topping off is not a good idea and your professional annalisess brought ir home for him. Again thank you.

  3. Michael E Heis

    So what fill rate should I use Mr. “expert”? The slowest one which will fill the tank the most or the fastest one which will fill it the least? Oh yeah you don’t know and that blows your whole argument out of the water.
    A slow fill would more “top” off your tank, so that would cause your SEALED carbon canister to leak gas out? ROLMAO don’t you know what SEALED means moron?
    More urban legend crap being spouted by people just following someone’s agenda and reading their talking points.

  4. Anna

    I didn’t have any idea about this. I got my Toyota Corolla CE in this September and from then everytime to topped up the gas tank by 5 litres more gas. Definitely I am not going to make this mistake ever again. But, I am concerned if it has damaged my car already. I usually take gas when the tank is half full and half empty and in average in take 3 to 4 times in a month.

  5. Laura

    My word, people. Topping off doesn’t mean filling your tank. It means letting the fuel pump automatically fill your tank until it turns off, and THEN pulling the trigger a few more “bursts” (often to “round off” the price, or just to get a “little more” gas in the tank). It’s FINE to fill your tank as often as you like, so long as you stop when the pump clicks off.

  6. JD

    Psh, done this for more than 3hrs now, guess what? My car still runs as new. Of course I also take good care of it in Every aspect, but here’s the thing. By adding the extra gas, I dnt “waste” money as you claim here, but on the contrary I save a lot of it. For instance, at current gas prices (4$/gal average) I can literally go from LA to Palmdale in California (that’s over 60 miles!) for just 5$-7$ max. 7$!! (Which is less than 2gls) Before I discovered that, I used to spend upwards of 20$ so you tell me how exactly am I wasting my money? Saving A Lot on gas is what I’m doing. But to each their own. I drive an 06 Toyota Corolla CE btw, but I feel it more like a prius now ;)
    Quick tip, another thing I do is the oil change every 5k/M instead of the old fashioned 3k/M. 2000 or newer cars can go longer without an oil change, but I bet your mechanic wnt tell you that go figure why..
    My advice, go with your gut and Definitely take good care of your car (do the require maintenance timely) if you really want it to last. Best to you all.

  7. keith

    My concern is, would my gas tank explode in hot weather if it’s full,
    I just read a warning by an oil mogul in Jordan, Middle East not to fill
    The tank for it might explode, we are expecting a heat wave next weak,
    The way I took the warning gas prices might be going up and he don’t
    Want us to fill up right now, waiting for an answer.

    • Chris Burdick

      I don’t know this for a fact, but I’d say that’s incredibly unlikely. I don’t think I’ve ever heard of that happening and there are safeguards in place for that kind of thing.

  8. Aaron407

    They left out the details, but topping off above where it automatically clicks off is definitely something to avoid. The problem is with the evaporative emissions system. There is a vapor hose that connects from the top of the tank to a charcoal canister. Normally, vapor during filling and while driving is collected inside of this canister, and a purge vent under the hood pulses to allow some of the vapor to be drawn by engine vacuum into the intake and burn in the engine. The commanded purge is the highest right after you fill up when the highest level of vapor is present. When you ‘top off’ your tank, you risk having liquid gasoline make its way into the charcoal canister and inhibit the normal operation of burning off vapors (since vapor can’t easily flow through a canister full of fluid gasoline), and can build up additional pressure inside the tank. One of the most common symptoms of a problem with this system, whether there is a check engine light or not, is difficulty filling up. You will often find that it will click off when it’s far from being full, and getting it filled to the proper level means re-engaging the trigger many times. It’s more of a hassle than anything, and changing out the charcoal canister or either of the two solenoids/vents can be quite expensive if they’re tucked away behind the suspension, as is the case in many vehicles. However, if some people prefer to roll the dice, go right ahead.

  9. terry leon

    My husband just ‘topped off our 2006 Grand caravan and we died while driving! After research, it is very dangerous to do this….especially a car dying on a major highway! So we won’t be doing that again!

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