If you’re missing the gas cap on your lawn mower and you’re in need of a replacement, then you’re probably wondering if there’s a universal gas cap to solve your problem. If you head to your local lawn mower shop, you will see replacement caps hanging on the hooks that say they are universal, but does this mean they are right for your mower? Well, before you put a new gas cap in your shopping cart, let’s take a look to see if universal really means universal.
So…Are Lawn Mower Gas Caps Universal? (The Short Answer)
Lawn mower gas caps are not universal. There are a variety of gas caps available for lawn mowers to suit different gas tanks and engines. Lawn mower manufacturers use several designs, including threaded, winged, and various levels of vented caps. Each gas cap is specifically designed to match particular lawn mowers. The wrong gas cap can lead to performance issues and lawn mower damage.
The Different Types of Lawn Mower Gas Caps
So, as you can see, gas caps are not universal. There are a bunch of different options available that are all different in some way. Let’s take a look at the different gas caps that are available and work out which one you will need for your mower.
Threaded Gas Caps
Threaded gas caps are similar to what I would describe as a nut and bolt cap. The gas cap is the nut, and the gas tank is the bolt. Both have threads that fit inside one another and tighten together with a rubber washer between the two to make a tight seal.
Winged Gas Caps
The winged gas cap is a bit of an older design and is more common on metal gas tanks. The cap has two lugs on the underside that fit into two holes in the gas tank opening. Again, these gas caps have a rubber washer that makes the seal.
Vented Gas Caps
Vented gas caps are not a design by themselves but a feature of both threaded and winged gas caps. If you take a closer look at a lawn mower gas cap, you’ll see that there is a small hole that allows air to enter the gas tank to prevent a vacuum from forming. This vent hole will vary between lawn mowers.
A push mower with a small engine will usually have a very small vent, whereas a larger riding mower with a bigger engine will have a larger vent. This difference in vent size is due to the bigger engine using up gas quicker and pulling gas from the gas tank faster.
The terms “one size fits all,” and “universal” really aren’t correct when it comes to lawn mower gas caps. For example, most push mowers and self-propelled lawn mowers have gas caps that are about two inches across. Meanwhile, ride-on or zero-turn mowers can have gas caps that are five or six inches across. So, size definitely does matter when it comes to gas caps.
Thread & Wing Size
Once you have worked out whether you need a threaded or a winged gas cap and what size you need, you’re then going to need to make sure that either the threads or the wings are the right size. More often than not, the threads of lawn mower gas caps are different sizes, as are the size of the wings on winged gas caps.
Why Buying the Right Gas Cap is Important (Problems It Can Prevent)
So, what happens if you use the wrong gas cap? Well, you’ll likely face some problems. Other than the universal gas cap not fitting correctly, there are some other issues you might run into. Here’s what you could encounter if you use the wrong gas cap.
- Damage to the Gas Tank
- Gas Tank Vacuum
- Spluttering Engine
- Stalling Engine
- Gas Spillage and Lawn Damage
Can You Use a Universal Gas Cap?
So, if you are looking for a lawn mower gas cap replacement, I would recommend that you track down the specific cap designed for your lawn mower.
That being said, if you buy the correct universal gas cap, then it can work. Usually, if you read the packet that they ship in, you’ll see that they will actually work with particular makes and models. This is why you’ll see different “universal” gas caps available.
For example, Craftsman, Husqvarna, John Deere, and MTD lawn mowers with a 2-1/8″ diameter gas tank opening use the same threaded vented gas cap for some of their lawn mower models. So while not all universal gas caps will fit your mower, you can find the right one that does.