Driving Without a Gas Cap – How bad is it?

Gas tank of a red car open ready for refillBehind a little metal door on one side of your vehicle hides the gas cap. From trucks to cars and everything in between, all vehicles that run on fuel have this cap. It’s an important one too, as the gas cap keeps dust, debris, and dirt out of the gas tank, preventing the contamination of your fuel. Should you lose your gas cap, are you okay to drive without it?

Driving without a gas cap is generally fine, at least for a little while. There’s no risk of noxious gas fumes getting into the passenger cabin. Also, due to a flapper valve within the vehicle, gas won’t leak even without a cap. That said, going too long without a gas cap could hurt your fuel efficiency and even damage the engine, so don’t delay in getting a new one.

In today’s post, we’ll tell you everything you need to know about your gas cap. From why and how it disappears to what to do if dashboard lights turn on after your gas cap goes missing, you’ll be ready to handle this small but inconvenient problem.

How Can You Lose Your Gas Cap?

First, let’s address a question we’re sure is on your mind. What happens to the gas cap that causes you to lose it in the first place?

There are all sorts of situations that can transpire. If you live in a state where you fill your own gas, then you could forget to reattach the gas cap after a standard fill-up. Perhaps you live in Oregon or New Jersey where you can’t pump your own gas. In that case, then the onus would be on the gas station attendant, who must have forgotten to reattach the gas cap at the pump.

Also, gas caps don’t last forever. Each time you unscrew and screw yours back on, that's more wear and tear the cap sustains. After a while, it might not tighten the way it once did. You also won’t hear that click of a secure gas cap.

While you should replace yours at this point, if you don’t, you could possibly lose the gas cap since it’s no longer attached properly.

Is It Dangerous To Drive Without A Gas Cap?

Gas cap of a white car open and waiting for a fill up

Most of the time, you won’t even realize that your gas cap is gone until the next time you go to fuel up. Then you’ll see when you open that little metal door that your gas tank is just sitting open.

Immediately, you’re going to have some concerns. What about fumes traveling into other parts of your vehicle, such as the passenger cabin? After all, besides keeping the gas itself uncontaminated, another duty of the gas cap is to manage your car or truck’s evaporative emissions system. Without this system, fuel vapors are passed into the atmosphere.

Don’t worry, as driving without a gas cap is not going to fill your vehicle with fumes the moment you turn it on.

Okay, what about fuel leaks? With nothing capping up your gas tank, won’t sudden maneuvers cause the gas to spill? Not at all. Your car or truck’s flapper valve prevents fuel from going where it shouldn’t. You do want to keep any heat sources away from the fuel intake though, as that could ignite the fumes and cause a major fire if not an explosion.

That’s the only real danger you have to worry about when foregoing a gas cap, at least in the interim.

Can Driving Without A Gas Cap Trip The Check Engine Light?

You get in your car one day and, as you’re driving, you notice the dreaded check engine light come on. You try to ignore it until you get to your destination, and then again when you’re driving home. However, after several days with no signs of the light turning off, you panic. Why is this light on?

There are all sorts of reasons the check engine light may appear, such as oxygen sensor issues, a broken catalytic converter, mass airflow sensor damage, problems with the wires or spark plugs, and even possible engine trouble.

Luckily, in your situation, you can more than likely rule all the above out, as the check engine light also appears if your vehicle’s gas cap is very damaged or missing. Even if you fix the gas cap issue, the light can still persist, in which case, you might have to take out your car battery to reset the light.

If the check engine light won’t quit after that, then perhaps the problem is grander than merely your gas cap.

How Long Can You Drive Without A Gas Cap?

If you want that pesky check engine light to finally disappear, then it’s better you don’t drive too long with your gas cap missing. It’s true that this might not be a very serious issue, but it’s one that can have long-term consequences if you’re really good at pretending the check engine light isn’t on.

It’s possible that the engine could eventually be wrecked. Also, your vehicle’s fuel efficiency will drop.

Once you realize your car’s gas cap has gone rogue then, make a plan to get a new one that same week.

Where Can You Get Your Gas Cap Replaced?

One place you can go for your replacement gas cap is your local mechanic. According to Repair Pal, you may pay $74 to $80 for a new gas cap, which includes the price of parts (about $57) and labor ($17 to $23).

If that’s too expensive, you can also shop for gas caps on Amazon, such as this one from Gates. An Amazon’s Choice product, the gas cap is a bargain. You can choose from a variety of vehicle makes and models when ordering your gas cap, so double-check that you get the right cap.

Click to see more on Amazon.


Gas caps, which cover your gas tank, are lost all the time. Sometimes the cap is just too old to hang on and other times it falls off, unbeknownst to you.

While you can get away with driving without a gas cap, you should only do so for a little while. It’s possible to accrue damage to your engine as well as experience a decrease in fuel efficiency if you go too long without the gas cap.

Share this article

One comment

Leave a Reply

Your email address will not be published. Required fields are marked *