Are Gas Caps Universal
Auto Parts,  Cars

Are Gas Caps Universal?

Almost every car on the road uses gas to fuel the engine and make the car move (electric cars are the exception). With every car is a fuel tank, and the entry point that all cars have is a gas cap. But, the gas cap is a flimsy piece on the vehicle and can be easily lost if not properly taken care of. If that happens, how difficult might it be to replace it?

Are gas caps universal? There are different types of gas caps, ranging from slow-release to cap-less. However, the gas caps for all types of vehicles are made to be universal and can fit to cover the gas tank in any vehicle.

Now that you know, you may be thinking that you can just plug and replace a gas cap for a lost one on your vehicle. While that is true, there are plenty of complications that come along with trying to replace a lost or damaged gas cap. Plus, gas caps are so much more than a piece of plastic that stops gas from leaving the gas tank.

The Purpose of a Gas Cap    

Fuel Fill Inlet Closeup gas cap

Gas caps are a small part of the vehicle but have more functions than you may realize at first. Obviously, the gas cap is essential to keep the gas inside the gas tank. It is the stopper for gas leaking out of the tank through the fill-hole. But there are more functions than that.

Another purpose is to keep other outside elements from entering into the gas tank. If fuel is mixed with other liquids or debris, then there can be dire consequences. While most vehicles are also equipped with a little door on a hinge that covers the gas cap and fill-hole, the gas cap acts as a last line of defense to prevent outside elements from coming inside.

An additional purpose of a gas cap is something that you may not even realize. Gas caps are essential to a car’s fuel efficiency.

Without a gas cap, there are gas vapors that leave the tank and go into the atmosphere. This not only damages the atmosphere, but it also takes away from the vehicle’s fuel efficiency. The less gas in the tank being used by the vehicle means the vehicle loses its fuel efficiency.

This can be a huge difference for vehicles in their ability to be as fuel-efficient as possible. If your gas cap is damaged or not even in use, a car could lose up to 30 gallons of gas per year, which can translate up to hundreds of dollars a year for people.

The Gas Cap Evolution

The tiniest of plastic on a vehicle may not seem like a modern marvel, but the evolution of the gas cap has quite a history. The year to keep in mind for big gas cap changes is the year 1970. That year, the Environmental Protection Agency (EPA) started to enforce a new vehicle emissions policy.

The EPA had done some studying of ground-level ozone layers and realized that the cause of the damage to the ozone layers were fuel vapors. Therefore, they implemented changes that would directly affect fuel vapors and try to change the course. Congress implemented the first Clean Air Act. The first Clean Air Act called for a reduction in auto air emissions by 90% by the year 1976.

In 1971, all licensed vehicles in the United States had to have evaporative controls built into their fuel systems. The first measure: the gas cap. The cap helped prevent gas from spilling out of the tank. Along with that, cars also started to use a charcoal canister to control vapors and reduce emissions into the atmosphere.

As time went on, the fuel vapor controlling measures tightened up, and by the mid-1990s, fuel vapor controls were more than 50 times those in 1971.

Another historical point in the gas cap history is the invention of the Onboard Diagnostics System (OBD). This system was invented in line with the changing rules about fuel efficiency and gas vapor emissions. The OBD System was built into the cars themselves as a way to track and monitor how well the engine is performing along with other systems in the vehicle.

In 1990, the Clean Air Act called for the new systems of Onboard Diagnostics, called OBD II. OBD II was designed to help test the fuel system by pressurizing it or applying a vacuum. Then, it would measure even the slightest changes that could be a sign of leakage and the potential loss of fuel vapors.

All of these new measures were put into place to save the environment, but they also saved people money. Earlier, the article mentioned that people with faulty gas caps lose about 30 gallons of gas per year. Over the entire country, though, at the turn of the century, roughly 17% of vehicles on the road had faulty or were missing gas caps.

That figure, calculated by the Chicago Tribune, roughly translates to Americans wasting over 9 million barrels of crude oil and losing over $220 million in one year.

The Different Versions of Gas Caps

While gas caps all look about the same in modern times, there have been a few subtle changes to the gas cap that are significant. The first and most noticeable is the plastic part of the cap that is inserted into the tank.

Prongs to Spirals

For older vehicles, their gas caps may look like two plastic prongs. This was a primitive measure to try and keep vapors from being released into the atmosphere. Nowadays, gas caps are more tubular, with spiraling threads to ensure as tight of a seal as possible.

Cork & Cloth to Synthetic Sealants

The sealing materials have also changed with time. Initially, cork or cloth gaskets were used to ensure the seal was fitted with the gas cap. But, because wear and tear plus chemical reactions, those types of materials tended to default over time.

In modern times, materials like neoprene or polyurethane are used with better resistance measures to ensure a tight seal.

Tighter Seals

Also, changed from previous times is the amount of times you have to turn the gas cap in order for a tight seal to be ensured.

Previously, people would have to turn the cap until the sound of clicking was heard, therefore indicating a tight seal. Now, most modern gas caps require a simple, 1/8 turn to hear one click and ensure a tight seal.

Slow Release Feature

Another new feature on gas caps is the slow release feature. Some gas caps have a warning label on them, stating, “open slowly.” This is to ensure that vapors are released slowly and not in a sudden poof. This is especially important on warmer days because gas is more susceptible to being turned into vapors.

Gas Cap Keys

There are also versions of gas caps that can be locked with a key. These gas caps do not typically come with a new vehicle and are usually replacement gas caps. They work just like any key entry, simply put the gas cap on, tighten until the clicks sound, and then lock it with the key.

Cap-Less Gas Caps

For those driving brand new vehicles, usually a 2019 model or newer, you may find that there is not even a cap anymore when you open the gas valve. This is the newest version of the gas cap, the cap-less gas cap.

The new cap-less gas cap eliminates all of the hassles of turning and taking off and putting on of the old gas cap. This can be useful if a person has arthritis and has trouble taking off and putting on a gas cap. It is also helpful in keeping the stench of gas from coming in contact with your skin or clothing and ruining the inside materials in your vehicle.

The way it works, the cap-less gas cap, is it acts as a trap door. When you put the fuel nozzle into the trap door, the sides swing open, allowing the nozzle to go directly into the gas tank and fuel up.

It also prevents anyone from attempting to siphon gas out of your vehicle. This is because the cap-less gas cap uses a fuel-filler neck that prevents someone from shoving a garden hose or other plastic pipe into the gas tank and taking out the gas.

There are negatives associated with the cap-less gas cap, though. While there may be less gas smell on your person after filling up, the cap-less gas cap system actually increases the smell of gas inside your vehicle.

Other negatives involve crises situation. If there comes a time you need to fill up your tank from a gas canister, you will need to use the specialty-made funnel provided by the vehicle’s seller. This can also create a gas smell in your vehicle after use.

The other negative situation where a cap-less gas cap may be a negative is when you do need to siphon your own vehicle (for fuel for an emergency fire or generator). There is no way to get the fuel out of your own vehicle to use it in other ways.

When Should You Replace Your Gas Cap  

Gas caps seem like a part of the vehicle that never really needs to be replaced, but they actually do have a mileage limit before wear and tear typically breaks them down. Depending on the brand, the time to start thinking about changing the gas cap on your vehicle is usually around the 50,000-mile range.

How to Tell if Your Gas Cap is Faulty    

 Now that you know when to potentially change your gas cap, how do you actually tell if it does need to be changed? There are several factors that can point to a new gas cap being needed on your vehicle.

The first indicator would be your check engine light illuminating. While this could indicate that your gas cap simply is not on tight enough, it could also be showing that your gas cap is faulty, and your vehicle is losing fuel efficiency. The best way to check would be to either take your vehicle to a mechanic, or to an auto-body store where most will run an electronic test to figure out the issue with the vehicle.

Another way to tell if your gas cap is faulty is to do a self-evaluation of it. Simply inspect the gas cap and look to see if there are any cracks in the filler neck (the plastic part of the gas cap). Also, check the threads and make sure they are not worn down, therefore creating a loose connection once reattached to the tank. The seal is another part of the gas cap that needs to be inspected.

An expensive way to tell if your gas cap is faulty is during a state inspection. Gas caps are now becoming a part of the yearly inspection required by every state to determine if the vehicle is safe enough to be on the road. Vehicle emissions and fuel efficiency are two factors that are directly impacted by having a faulty gas cap.

Using your senses can also be a good way to tell if your gas cap is faulty. If there is a potent gasoline smell in your vehicle, then your gas cap may have some cracks or faults in the filler neck. This is because the cracks in the filler neck might be allowing fuel vapors to leak out and be released into the air.

Can You Drive Without a Gas Cap?      

Driving your vehicle with a piece of it missing may seem confusing or scary. And even such a small piece like a gas cap can make a difference in how the vehicle drives and performs. But, you can drive without one attached to your vehicle.

For most cars, though, a gas cap can trigger a check engine light if it is not properly put on and locked into place. But the problem is, a check engine light does not specifically point to which part of the vehicle is the problem. Therefore, you may have to take the vehicle into the shop to get it checked out, which could cost you hundreds of dollars, for as simple of a solution as tightening your gas cap.

But, overall, there is most likely no harm in driving without a gas cap on your vehicle. On newer vehicles, there are special valves built in that will not allow any gas to spill out of the tank. Driving without a gas cap also will not do any damage to the vehicle’s engine.

Replace your gas cap as soon as possible though. It is important for the environment, safety, and to prevent loss of fuel.  

Cost of Replacing a Gas Cap     

Gas caps are essential to the vehicle and making sure it runs as smoothly and as efficiently as possible. But if you do lose your gas cap, or if it becomes damaged, you should find a replacement and do it as quickly as possible.

But where do you find new gas caps? Depending on how dire the situation is, there are plenty of places to find one.

If you are really in a pinch, say on a road trip, and your gas cap becomes damaged or lost, some of the chain gas stations (Sheetz, Exxon, 7-Eleven, etc.) might carry gas caps in their stores. Otherwise, you can use a rag to stop fuel from spilling out and preventing fumes from escaping the tank. This should be a stop-gap fix to tide you over until you get to your destination, or until your trip is over.

If you are at home and you lose your gas cap, taking your car to your dealership or mechanic could be expensive, depending on whether your mechanic will have to do an entire inspection of the vehicle. But, you will have the peace of mind knowing that a professional is replacing the part and doing it properly.

Your local Walmart, or another box-chain store with an automobile section, should also carry a wide selection of different gas caps for your vehicle. As well, stores like Napa Auto Parts, Pepboys, or Autozone also will carry gas caps and have employees that have the knowledge to show you which ones are the best for your type of vehicle.

One thing to look for when replacing a gas cap, besides just overall price, is that the gas cap actually fits with your vehicle. The easiest way to determine this is to try and tighten the new gas cap in the tank, and if it does not click, it does not fit. The check engine light should also be an indicator as to whether the new gas cap fits as well.


So, in the end, gas caps serve a more purposeful role in the vehicle than many people realize. They are intended to help ensure the vehicle is as fuel-efficient as possible while keeping harmful fuel vapors from being released into the atmosphere.

Gas caps have come a long way, with the EPA in 1970 really pushing for changes to the atmosphere and changing vehicles’ impact on the environment. As time evolved, gas caps have become more technologically advanced, even to the point where they are no longer needed on vehicles.

Always be sure to consistently check your gas cap to make sure there are no cracks or damage to the filler neck. And if your check engine light comes on, it could be as simple of a fix as replacing your gas cap.