Much like your car engine, your lawn mower engine requires important tune ups and maintenance. This will keep your mower running well and save you a lot of the headaches that come from delayed maintenance. One key maintenance requirement for any combustion engine is regular oil changes, but it’s important to know what motor oil to use in your lawn mower.
The Short Answer
Most modern lawn mowers have a 4-stroke engine (if your mower has an oil dipstick, then it’s 4-stroke), and for this type of mower most SAE-30 motor oils will work well. 2-stroke mowers require a special mixture of gas and oil to function properly. Either way, I recommend that you consult your mower’s owner manual to determine the best type of oil for your mower’s engine.
Using the wrong kind of oil can result in engine damage, so keep reading if you’d like to learn more.
When to Change Your Mower’s Oil
It’s my recommendation to change the oil in your mower when you first get it out of the garage in the spring, or right before you put it away for the winter.
If you use your mower year round, then aim to change the oil every 20 to 50 hours of use.
Lawn Mower Oil Basics
There are different types of motor oil for lawn mowers and other small engines. Even the climate you live in can affect the type of oil that you should use.
It’s important to understand what the differences are. This will help you to choose a motor oil that is safe for your lawn mower.
The last thing you want to do is use the wrong oil and ruin your engine.
Different Strokes for Different Folks
The first distinction that is important when deciding what oil to use in your mower is whether it is a 2-stroke or 4-stroke engine.
There are key differences between these two types of engines that factor into what oil to use.
The most important thing to know is that a 4-stroke engine has separate compartments for gas and oil while a 2-stroke does not. This means that a 2-stroke engine requires a premixed ratio of gas and oil within the same compartment.
In general, a 2-stroke engine is a small motor, while a 4-stroke engine is more complicated – more like the motor in your car.
These days most modern lawn mowers are 4 stroke engines, but if you’re not sure what type of mower you have just look for an oil dipstick. If your mower has one, it’s a 4-stroke engine.
Different Types of Motor Oil
Many people believe that all motor oils are the same and can be used interchangeably with any type of motor, but that is simply not the case.
Many small motors cannot take automotive oil due to it being a thicker consistency. It can end up clogging different parts of the machinery, which is just the opposite of what motor oil is intended for.
Conversely, small motor oil will be too thin to properly lubricate a larger engine.
Motor Oil to Use in Lawn Mowers with 4-Stroke Motors
Motor oil found in an auto parts store or gas station can usually be safely used with a 4-stroke engine.
These engines are common on tractors, riding mowers, and larger push mowers. However, some engines don’t do well with certain oil additives, so it is still good to check the owner’s manual to be sure.
A pretty safe bet could be SAE-30 oil if you’re in a pinch. This type of motor oil is readily available and used a lot.
The best way to check the oil level in your mower is by pulling the dipstick from the oil compartment. Do this when the machine has not recently been running. Wipe it, re-insert it, and check then check the level when you pull it out again.
This will give you the most accurate measurement and let you know if you have added enough oil.
An average push mower with a 4-stroke engine may need up to 18oz of oil. A large riding mower engine can require up to 64oz.
You never want to over-fill your lawn mower with oil or your mower may start to smoke. I always recommend topping up your oil slowly and checking with the dipstick until you get the level just right.
Motor Oil to Use in Lawn Mowers with 2-Stroke Motors
Smaller mowers and other small machines likely have 2-stroke engines, which need a specific ratio of gas and oil within the same chamber. The ratio can range from 20:1 to 50:1 depending on the motor. This information can be found in your owner’s manual.
Oil for small engines is lightweight and should have APR performance ratings of SF, SH, SG, or SJ to indicate that they are compatible for 2-stroke motors.
It is also possible to find premixed formulations of gas and oil based on your machine’s needs as outlined in the owner’s manual.
Small motor oil is found in the garden department of hardware stores or auto parts stores, separate from automotive motor oil.
Interestingly, motor oils work best in certain climates depending on the temperature, which is particularly important for 4-stroke motors.
For example, SAE-30 oil works best between 40 and 100 degrees Fahrenheit.
If you need to operate an engine in colder conditions, then a synthetic oil or other formulation such as SAE 5W 30 may be necessary for optimal operation of your engine.
Companies like Briggs and Stratton endorse synthetic oil. They love its quality, as well as its wider range of acceptable temperatures.
In my opinion you can go with old-fashioned motor oil or synthetic, but I recommend staying consistent in what you use.
Check the Manual
Before you decide what motor oil to use in your lawn mower, check your lawn mower owner’s manual.
The manual will tell you exactly what kind of oil is ideal for your specific machine.
And even if you got your mower used (without a manual) or misplaced your mower’s owner’s manual you can quickly find it online with a search for your mower’s make and model number.