Can Lawn Mower Gas Go in Cars?

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Your car is running low on gas, but your lawn mower is full. The question now arises, can you put lawn mower gas in a car? And what happens next? Is it all good or cause major issues? I am going to answer that question as well as related topics. Without further ado let’s get into it.

Lawn mowers run on the same type of gas as cars. Keep in mind though that while cars can run on gas with 15% ethanol, lawn mowers can only handle 10%.

Are Lawn Mower and Car Gas the Same?

Most lawn mowers use the same regular unleaded gas that cars do. When you go to a gas station to fill up the tank, that stuff will also work on mowers.

This also means you can use lawn mower gas in your car. Note that I said “most”, because there are exceptions which I will get to shortly.

The bottom line is that if your lawn mower was made any time during the last 12 years, it is likely a 4-stroke and is compatible with car gas. You can go to a fuel station, fill a canister and pour it into your riding mower.

This assumes your car uses regular unleaded. If your car uses a u special fuel or has more than 10% ethanol, your lawn mower won’t run. Even if you get the engine to start, there could be long term damage due to the high ethanol content.

Do All Lawn Mowers Run on Car Gas?

A 4-stroke lawn mower runs on the same gas as cars. Most lawn mowers today are 4-stroke such as the PowerSmart Push Lawn Mower, so gas compatibility is not a problem. But if you have an old 2-stroke lawn mower, things can get complicated.

A four-stroke lawn mower has separate compartments for oil and gas. So you can put car gas in the reservoir and it will run.

A 2-stroke mower on the other hand, requires a mixture of gas and oil. You have to add oil to the mix before the engine can run.

Second, lawn mowers can only run on 10% ethanol. Anything higher can damage the engine.

Most cars can run on up to 15% ethanol, but for lawn mowers it is 10%. Keep that in mind if you are going to put your car gas in the mower.

Ethanol is a bigger problem with 2-stroke lawn mowers than 4-stroke. But it is still better to keep it at 10%.

To keep it simple:

  • if your car gas has 15% ethanol, do not put it in your lawn mower.
  • If the gas is 10% ethanol, it should work with modern 4-stroke lawn mowers.
  • Now if you have an old 2-stroke model, you have to add oil to the mix.

Using the right gas is important if you want to use a lawn mower to pick up leaves for instance LNK So check if your lawn mower is 4-stroke or 2-stroke.

To find out, check the engine. If there are tanks for the gas and oil, it is 4-stroke. If it is just one, you have a 2-stroke lawn mower.

Why Too Much Ethanol is Bad For Lawn Mowers

If you want to avoid the ethanol problem completely, you can use 100% ethanol-free fuel. If you are using gas with ethanol, read on to find out why too much is bad for lawn mowers.

If the ethanol is 10% or less, your lawn mower is fine. Anything higher and it will cause long term, possibly irreparable damage. Here’s why.

Ethanol draws water from the air. When you run a gas lawn mower, the ethanol causes water to mix with the fuel. A bit of gas and water mix isn’t bad, but if it is higher than 10%, problems can arise.

High ethanol levels lead to engine deterioration. Rust and corrosion build up, clogging the carburetor. It spreads to the spark plugs, cylinders, blade, fuel tank etc.

This is why it’s a bad idea to let gas sit in lawn mowers for a long time. After several weeks, the unused gas turns gummy and clogs the engine. If the gas is rich in ethanol, the problem gets worse.

You have two options: empty the fuel tank before storage, or put a fuel stabilizer like STA-BIL 360. This will keep the fuel from turning into a sticky substance. But this isn’t going to solve the ethanol issue. To avoid that, just use gas with 10% or less ethanol.

Most cars built after 2001 can handle E15 (ethanol 15%), but lawn mowers are designed only for E10. If you put high ethanol gas in a lawn mower, the engine could suffer major damage.

Can Cars Use Lawn Mower Fuel?

All 4-stroke lawn mower gas can be used in cars. A 2-stroke lawn mower uses a mixture of oil and gas so it is not compatible with cars.

If you have old gas sitting in the lawn mower, you are probably wondering if it is safe to use on your car.

If gas is no more than 60 days old, your car will be fine. Anything older than that and there is the risk of engine clogging and other issues. Actually the same can be said for lawn mowers. If the gas is old, replace it.

Do Lawn Mowers Require Premium Gas?

Lawn mowers only need regular unleaded gas, with an 87 octane rating and 10% ethanol or less. Most will work with premium gas, but don’t expect any major performance boost.

Most outdoor power tools state that 87 octane is the minimum rating required. You might think that getting higher octane gas is better.

But that is not always the case. Higher octane gas oes not really improve how your lawn mower works. In fact, some small engines prefer only an 87 octane rating.

A 2-stroke lawn mower also uses regular unleaded gas. But in this case you have to add oil because two-stroke engines require a mixture of oil and gas.

Frequently Asked Questions

Can old car gas run on a riding lawn mower?

Yes, as long as the gas is no more than two months old. The fresher the gas the better. If you are going to store your lawn mower for the winter, remove the old gas or put fuel stabilizer in it.

But for the best performance, use fresh gas for your lawn mower. Replace it every 30 days so it doesn’t turn into sludge.

Can I use my car’s premium gas in a lawn mower?

It should work with most riding lawn mowers, but check the operating manual to be sure. Keep in mind that premium gas is not going to result in any major improvement. These 4-stroke lawn mower engines are optimized for regular unleaded so other gas types will not do much for it.

Is ethanol-free gas better for lawn mowers?

Anything higher than 10% ethanol is bad for lawn mowers, everyone agrees on that. But the benefits of ethanol-free gas is up for debate.

Ethanol-free gas is not going to harm your lawn mower, but is it going to boost performance? The results have inconclusive so far. For many people, E10 gas is fine.

Do 4-stroke and 2-stroke lawn mowers use the same gas?

Yes, but there is a big difference between the two. A 2-stroke engine requires mixing oil and gas, so pouring car gas into the tank is not enough. A 4-stroke engine does not mix oil and gas. You can pour car gas in it and the engine will start up.

Can I mix old and new gas in my lawn mower?

No. Gas degrades over time, and when you add new fuel it can cause instability. The engine could sputter or not run at all. Old gas might have turned viscous, and putting new gas in just makes it harder to clean up.