Can You Use Car Oil in a Lawn Mower?

by Synthetic Oil | Last Updated: October 25, 2021

If you have a yard with a lawn, then you usually own a lawn mower. Maintaining your yard is just as important as keeping your lawn mower in tiptop shape. Since lawn mowers have an engine like a car, it is going to need lubrication once in a while to keep the engine running clean and smooth. Can you use car oil in a lawn mower to keep it running? Or do you need another kind of oil?

Here is what you need to know.

Lawn Mower Engines and Oil Quality

What kind of lawn mower do you have at your home? Smaller engines in push mowers tend to require a different type of oil than what goes in a larger riding mower.

Generally, lawn mowers need an oil that is higher priced than conventional oil for cars, such as SAE 30 motor oil. However, it is recommended that you take a look at the owner’s manual to see exactly what your lawn mower needs. If in doubt, consider the engine size and style.

The same rule applies to your car. You should always use the recommended oil for the engine in your vehicle. If you are using high-quality oil for your car, it will also work in your lawn mower. Simply avoid using low-quality oil, and the engine should operate fine.

Different Kinds of Oil Available

What kind of oil is available for lawn mowers or small engines? Turns out, you have some options.

Car Oil

In the past, car oil was oil and additives, but it wasn’t the best for your engine. Now, motor oil is much more elegant and uses less mineral oil. There are friction modifiers, detergents, corrosion inhibitors, and much more in the oil to give motors more longevity. Since oil blends these days are proprietary, it is best to read what is included in the formula to find out if you can use it in your lawn mower. For instance, some car oil formulas are only for new car models while others are meant for high mileage.

Car oil will cool and clean any engine that it circulates through, including your lawn mower. So yes, you can use it.

Two Stroke Small Engine Oil

You are going to need two-stroke (2-Stroke) small engine oil. This kind of oil will be a mixture of castor oil, synthetic oil, or a blend of mineral and synthetic oils. It also has additives, like detergents, and will be mixed in with gasoline. Put the oil directly into the gas tank.

For air-cooled two-stroke engines like this, you can’t use car oil. What happens if you put car oil in a two-stroke engine, you ask? Ash will build up around the spark plug, and residue will pile up around the combustion chamber. Furthermore, many of the additives in car oil will interfere with the function of a two-stroke motor.

Four Stroke Small Engine Oil

Mineral oil and synthetic oil are two options for a four-stroke small engine. These blends for a four-stroke engine usually contain more zinc than standard car oil. The zinc is added to prevent wear and tear. You can also find an oil that has additives to clean the engine. Choose a four-stroke oil with the appropriate viscosity. That will help the engine run more smoothly in both cool and warm weather.

Like car oil, four-stroke small engine oil is designed to lubricate, cool, and carry gunk away from the point of combustion. Car oil can replace this kind of oil in a lawn mower, but the additives used in both are different.

Now for the caveat: You can only use high-end oil, such as 10W-30 or SAE 30. Newer mowers will work fine with either four-stroke motor oil, whereas older mowers might lose some power.

What Kind of Oil Do I Use in A Riding Mower?

Since your riding mower is more or less a vehicle, you should be able to use the same oil you do in your car, right? Well, as with everything else, it depends. The simplest way to know is if your riding mower has an oil filter. Inspect the engine of your lawn mower. If you spot an oil filter, then you can certainly use car motor oil, but again, it is going to need to be SAE 30 or 10W-30.

No oil filter? Select a non-detergent 10W, typically a 10W-30 will suit.

Can I Use a 5W Oil in a Lawn Mower?

Most manufacturers have formulated their synthetic 5W-20 and 5W-30 oils to operate fine in lawn mowers with an oil filter. The only difference is that, when 5W-30 is operated at a higher temperature, it will be thicker than 5W-20. Again, you should look at the owner’s manual to see which viscosity is most appropriate for your lawn mower.

Wrapping Up

Can you use car oil in a lawn mower? It depends! A two-stroke lawn mower motor cannot use car oil, because it will damage the engine. Four-stroke lawn mowers, however, can use car oil and will function without any problems. Most manufacturers will tell you what quality and viscosity of an oil is best for the lawn mower, but the most commonly recommended is SAE or 10W-30, which can be used in cars.