Can You Use Car Gas in a Lawn Mower? (Solved)

Car with nozzle of pump in gas tank

That age-old question, can you use car gas in a lawn mower?

It feels like something you should know, but it is often the case that people aren’t sure of the answer.

For the most part, the matter is fairly straightforward.

But as ever there are a few caveats!

We explain all here, so without further do, let’s jump in!

Can You Use Car Gas in a Lawn Mower?

Using regular car gas in a mower is fine in the short term, but might cause problems over a longer period of time. That is because car gas contains ethanol, and this can degrade parts of your mower with prolonged use. For peace of mind and to extend the life of your mower I would advise using ethanol-free gas.

In Most Cases Using Regular Car Gas in Your Mower is Fine

If you are going to be using your mower on a regular basis, as most of us do over the summer, then filling the tank with regular car gas should be fine in most instances.

When gas is constantly being cycled through the system of your mower, it will make very little difference what kind of fuel you use.

But You Might Need to Be Wary Of Older Engines

Most gas-powered mowers these days are 4-stroke, however, if your mower is older (15 years plus) it might a 2-stroke.

Two-stroke and 4-stroke machines have different fuel requirements.

If there is a place on your mower for gas and another for oil you have a 4-stroke mower and regular gas should be fine to use.

If you can only see one hole on your mower, it could be a rarer 2-stroke mower. 

Two-stroke mowers need oil mixed into the gas to lubricate it. Often older engines also struggle with regular gas as it has ethanol in it, which can harm the engine (more on this later).

In these circumstances, I would advise using an ethanol-free gas or a specially engineered fuel like Tru-Fuel.

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However Ethanol Free Gas is the Way to Go

So generally you can use car gas in your mower without worrying too much.

But if you want peace of mind and want your mower to run for longer without issues, I would always advise you to use ethanol-free fuel.

Regular gas has 10% ethanol in it and over time the ethanol can degrade the parts of your mower.

So what is so bad about ethanol?

Ethanol is hydrophilic. That means it attracts water.

As the gas is being burned by the engine, water enters your fuel system and is drawn into the gas.

This chemical mix of water and gas accelerates the corrosion of metal and rubber parts of your engine.

It can also dissolve deposits from the gas tank and fuel lines, which can clog your carburetor.

In the short term, continual use of regular gas is fine, but in the long term, it is a far better idea to use ethanol-free gas.

And the very worst thing you could do is leave regular fuel in the tank of your lawn mower long-term (ie over the winter).

Don’t Leave Fuel Sitting in Your Mower Long Term

Leaving fuel of any kind, regular or ethanol-free, sitting in your mower whilst your store it away for winter is a bad idea.

The fuel (especially regular car gas) can degrade and create serious problems for you when you go to start it up a few months later.

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What you want to do towards the end of the season is add a stabilizer to the tank.

Fuel stabilizers contain additives that are anti-oxidants, they take the oxygen that is in gas and prevent it from congealing and clogging up.

That means you can leave the fuel in the tank, safe in the knowledge that any potential damage it can do will be extremely limited by the stabilizer.

The very best stabilizers offer something called vapor technology. This doesn’t just treat the fuel, but also the air and vapor that floats above the gas in your mower’s tank.

For the Best of Both Worlds Try a Premixed Fuel

Cars at gas station

Premixed fuels, like TruFuel, are another excellent alternative to using regular gas.

TruFuel is an ethanol-free fuel with stabilizers in it. It won’t clog up your engine if left over the winter and will extend the life of your engine.

It is available in most hardware stores but is expensive.

Now of course this leads on to another question we should answer for the sake of thoroughness…

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Can Lawn Mower Gas Go in a Car?

Unless you have a 2-stroke mower, which uses gas mixed with oil as noted above, then you are good to put any leftover lawn mower gas in your car.

If the gas in your mower is aged gas, it won’t be great for your car, but it shouldn’t cause any long-term damage.

To be safe I would fill up your car with a good amount of regular gas and then pour any leftover gas from your mower into the car’s tank.

If the mower gas is old or contains some potentially damaging contaminants or particles then it will be diluted by the much large volume of gas already in the engine.

Also, of course, make sure your car isn’t diesel!

Final Thoughts

INFOGRAPHIC Can You Use Car Gas in a Lawn Mower

The infographic above gives you a quick overview, but…

Can you use car gas for your lawn mower? Yes.

Should you? Probably not on a regular basis.

Over time the ethanol found in regular gas can degrade your mower. 

If ethanol-free gas is easily available in your area, it is a much better bet than regular fuel.

So the key takeaways are:

  • Using ethanol-free gas will prolong the life of your mower.
  • Your mower will run just fine with regular gas, but you might encounter problems in the long term.
  • Older lawn mower engines might be 2-stroke machines and have different requirements.
  • If you are leaving fuel in your mower while it sits idle over winter add a stabilizer to it.

I hope this all makes sense and good luck!

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