Does Lawn Mower Gas Work with Cars?

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Gas lawn mowers are the most popular type because they offer a lot of power and versatility. But what type of gas do these power tools need? Can you use the same type that your car does or something else? If you are not sure what gas your lawn mower requires, this is the right place as those questions are answered.

4-stroke lawn mowers use regular unleaded E10 gas, which works fine with cars. As long as the ethanol level is no more than 10%, you can use regular gas. If you have a 2-stroke mower, you can use E10 but you have to mix it with oil.

Do Mowers and Cars Use the Same Type of Fuel?

Lawn mowers and cars can use the same type of gas, regular unleaded E10. In spite of what you may have heard or read, car engines and small engines like those on lawn mowers run on E10.

You can confirm this by checking the fuel requirements of your 4-stroke lawn mower. The PowerSmart Push Lawn Mower for example, runs on gas wit up to 10% ethanol. The octane rating recommended is at least 87.

Car and lawn mower engines are not the same, but they are both compatible with E10 gas. All modern lawn mowers run on 4-stroke engines which are deigned to handle ethanol. Unless you are using a decades old mower engine, it should have no problems with E10.

In fact, many 2-strok lawn mowers work with E10. Unlike a 4-stroke engine however you have to mix the gas with oil at a specific ratio. This ratio will be specified in the owner’s manual or the manufacturer website.

There are many types of gas, but regular unleaded 10 with a minimum 87 octane rating will be enough. Is ethanol-free gas available? Yes, but using E10 will not damage a lawn mower. Whether there is a performance boost with using ethanol-free gas vs. E10 will depend on the lawn mower.

Why High Ethanol Gas is Bad for Lawn Mowers

Using the right type of fuel is important, especially if you plan to cut tall grass. If your car runs on E10 regular unleaded, you can use that for your mower. But if it uses another type of gas or 15% ethanol, do not put that in your lawn mower.

If the gas is E10, that is fine for lawn mowers and cars. If it is E15 or higher, it will work for a lot of cars but not lawn mowers. While cars can handle this ethanol level, it will cause permanent damage to a lawn mower. There are many reasons why high ethanol is bad for lawn mowers and we will list some of them here.

  • Cars designed for E15 can burn fuel faster. Lawn mowers cannot do this.
  • The alcohol level in ethanol-rich gas is too much for lawn mowers. With E10 it is not an issue, but at a higher level, the alcohol can damage fuel lines and other engine components.
  • Ethanol retains water. At 10% or lower this will not be a problem. But at 15% or higher, water will settle on the carburetor and other parts of the engine. Over time this will cause corrosion and rust.

The good news is that E10 gas is widely available. You can find these in any gas station and use that to fill up your mower.

Do You Need Other Types of Gas for Lawn Mowers?

Regular unleaded will work just fine. You can use ethanol-free gas but it is not necessary. You can also use midgrade or premium gas, but it will probably not make much of a difference in performance.

Will a lawn mower run on high octane fuel? A lot of mowers are designed to run on 87 octane. Most will probably run on higher octane, but some actually run better at just 87 octane. There might be a cost, but probably not enough to warrant the additional cost.

To keep things simple here are a few guidelines.

  • If you have a 4-stroke lawn mower such as the SoarFlash 209cc, it will run on regular unleaded 87 octane E10 gas.
  • You can use E10 on 2-stroke mowers too, but you have to add oil.
  • Some specialized lawn mowers may require another type of gas other than E10. Check the owner’s manual.
  • The ethanol rating must never be higher than 10%.
  • While 87 octane is the minimum rating, some mower will not run any better on higher octane. It depends on the make and model.

A word here about storage. If you are going to store the mower for week or so, you can keep the fuel in the tank. If you are going to store it for 4 weeks or longer, empty the tank or add fuel stabilizer. This will prevent the gas from turning into sludge. Or you can just remove it before storing for the winter.

The Effects of Wrong Gas on Lawn Mowers

Using the wrong gas can lead to all kinds of problems, from light to serious. At the very least, your lawn mower will not start. The worst case scenario is the gas damages the engine and will require repair.

Sometimes the problems do not appear right away. For instance, you accidentally poured E15 in the tank. The lawn mower starts and cuts grass as usual. Everything looks fine on the surface. But inside, the ethanol is damaging the engine.

The more you run and burn high, ethanol fuel in the mower, the greater the damage. Eventually the mower will stop running.

If you accidentally used the wrong gas, turn the mower off and empty the tank. Do not attempt to burn the fuel off as that will make things worse.

The assist way to avoid this is to read the owner’s manual. The manufacturer will specify what type to use, the octane rating, ethanol amount etc.

Can You Put Lawn Mower Gas in a Car?

You can put 4-stroke lawn mower gas in a car. Most cars will also run fine for short distances with 2-stroke gas, which contains oil. Use 2-strok gas for your car for emergencies or short trips only because over the long term there could be damage.

As pointed out above, 4-stroke lawn mowers use the same gas as cars. You can use the gas for either one. While lawn mower gas has to be replaced every 30 days, it is not the case with cars. If you want you can use old mower fuel in your vehicle so it does not go to waste.

Two month old gas is okay for most cars, and it really only becomes a problem if the gas is a year old. But if we are talking about 30 day old gas from a mower, your car can handle that.

Ideally your car and mower should have their own gas supply. While they use the same type, it is better if each had their own. You should only use mower gas if there is an extra amount that was not used.

With 2-stroke engine oil it is a different matter. As you already know, these engines use a mixture of gas and oil. In an ideal scenario, cars should only use gas. But most of them will accept mixed oil. If you pour the 2-stroke engine oil and start your car, it will run without a problem.

But this is something you should not do over the long term. It is all right for emergency cases or short strips. But do not make this a regular thing. Since car engines are not meant to use this kind of fuel, there could long term potential damage.

Can using 2-stroke fuel damage car engines? For the short term no, but for the long term it might. If you are a car owner, there is no reason to take the risk. And if you have a 2-stroke lawn mower, maybe it is time to upgrade to a 4-stroke.