Topping off gas tank

Reasons To Avoid Topping Off Your Gas Tank

While urban legends about cars typically involve someone getting run over, others are a bit more mundane—but just as persistent even when proven to be false. Always heard you should warm up your car in the mornings before driving. Unless you’re driving a car from the fifties, that’s false. Spending more for high-octane fuel to clean the engine? Unless premium gas is recommended by your car’s manufacturer, you’re wasting your money.

Do you fill your tires to the maximum PSI according to the tire specifications? This misinformation is prevalent, but it’s a myth—always inflate your tires according to the vehicle’s specs (usually on a sticker in the driver-side door jamb). Do you top off your gas tank after the pump stops or pull out the nozzle enough to continue fueling before the pump shuts off? You may be causing more harm than good to your well-being, those around you, and the environment—and that’s no urban legend!

What Is Topping Off Gas?

Topping off a gas tank is when a driver continues to squeeze the trigger after the gas pump stops pumping. Another topping-off move is to slowly pull the nozzle out enough to reset the trigger. Whether you do it to squeeze out the last drop of gas or you have a thing for rounding up to the nearest dollar, overfilling your gas tank is a bad idea. There’s a reason gas pump handles have a rubber collar to cover the gas tank opening while you’re filling up. The collar is a safety measure to prevent gas vapors from escaping—the exact thing we do when we top off our gas tanks.

Why Is It Bad To Overfill Your Gas Tank?

According to the Environmental Protection Agency (EPA), topping off your gas tank doesn’t save money and can be a hazard to your car, other people, the environment, and you. Gasoline vapors can lead to health risks, cause air pollution, and even catch fire. Overfilling a gas tank can also cause the gas to overflow and pollute nearby groundwater, resulting in a hazard to wildlife. Topping-off can also damage your car or truck.

Consider some interesting math from Consumer Reports, and it’s evident how topping off the tank can be bad for your vehicle. Gasoline expands about 1% for every rise of 15 degrees Fahrenheit. In many climates, the temperature can vary by 30 degrees or more in a day. 30 degrees x 15 gallons of gas = expansion of more than a quart. The expansion can cause fuel to get into the charcoal canister that absorbs vapors, disabling it and creating a potential hazard.

What Happens When You Top Off Your Gas Tank?

Spilled gas, irritating vapors, and other hazards of topping-off are evident, but overfilling the gas tank can cause plenty of problems after you’ve driven away. When you fill your car up with gas, a charcoal canister collects the gas vapors to reduce hydrocarbon emissions. Modern vehicles feature a closed-circuit system that prevents hazardous vapors from escaping and turns the vapor into more fuel. Should you top off your gas tank even once, the vapor filter can be ruined. Without the filtration, a car will emit hazardous vapors, and the engine performance and fuel economy could suffer, leading to costly repairs.

Can Overfilling Your Gas Gas Tank Cause Check Engine Light?

Yes, but not always. If your check engine light comes on after pumping gas, the cause can often be an untightened gas cap. It could also be caused by topping off the gas tank. When the tank is overfull, the vapor intake hole can be covered, and the fuel can be sucked into the charcoal filter. Once fuel saturates the emissions filter and the check engine light stays on, it’s essential to have the issue corrected to avoid further damage.

How to Break the Gas Tank Topping Off Habit

Are you ready to change your bad fueling habits and put another urban legend to rest? For most drivers, knowing the truth may be enough to break the topping-off habit. Other drivers may need a little more incentive. If it’s time to buy another car, those drivers could invest in a cheap hybrid to break the pattern or a car with exceptional fuel economy. After all, the fewer times they pull up to the pump, the fewer times they’ll need to resist the urge to overfill the gas tank!

Car Time Supercenter is a local family-owned used car dealership in Tucson that can’t help drivers break bad habits. But we can help them find the ideal car or truck that fits their lifestyle and budget. Browse our online used car inventory to find the best fit for your driving habits, and we’ll take care of the rest with flexible financing and competitive pricing.

Shane Vossough

There are good reasons people will buy their next used car in Tucson from Car Time Supercenter. But I think we are one of the most trusted used car dealerships mainly because we treat everyone like family. My family has provided quality, dependable local used cars to Tucson customers since 1984, and I'm proud to be a part of our continued success. Like many family-owned businesses, I grew up going to work with my dad. Falling in love with cars was natural because of my father's passion, and eventually, I came to love the car business just like him. I officially joined the Car Time Supercenter team in 2012, starting in the finance department. Over the past decade, I've learned the used car business and how to treat customers from my family and industry resources. Today, I oversee marketing, social media, inventory, and reconditioning, so I play an essential role in delivering local Tucson used car buyers the best experience possible. I also help our family business keep up with the times while providing old-fashioned customer service. From attending NADA classes to becoming Allstate certified for back-end products, I continue to learn and add skills to serve our customers better.