Oil plays a critical role in the performance of a lawn mower engine. Whether it’s two-cycle oil for a two-stroke engine or standard engine oil for a four-stroke engine, without oil a lawn mower’s engine will inevitably overheat and fail. It might be a simple seize-up of the piston in the cylinder or a total failure in the engine block caused by a thrown rod.
What Is The Difference Between A Two-Stroke & Four-Stroke Lawn Mower Engine?
When it comes to lawn mowers, there are essentially two types of engines to consider. Each has its own strengths and weaknesses. It also affects the type of oil you need to use as well as how that oil is introduced to the engine.
A “Two-Stroke” lawn mower engine is simpler in design and engineering. It only goes through two cycles to completely deliver the pour the combustion chamber produces. This tends to translate into more power, more responsiveness and a generally lower initial cost.
The problem with two-stroke lawn mower engines is that they tend to be smoky, they are more prone to gumming up the carburetor as well as problems with the spark plug. Two-stroke engines also tend to be louder, which has started to move them out of popularity in suburban areas.
Two-stroke engines also need a special type of two-cycle oil that needs to be mixed directly with the gasoline. If you put standard SAE 10W 30 in a two-cycle engine it will not perform well and could be badly damaged.
You also need to take into account that there are different types of two-cycle oil and that different engines need different mix ratios. These days a lot of lawn mower manufacturers offer their own brand of two-cycle oil for their small two-stroke engines. Though you can usually get by with a generic version. Just look to make sure that it’s not marine two-cycle oil, and that it’s rated for “Air Cooled Engines.”
A lot of these oils will also be used for other small two-stroke engines in the manufacturer’s line. This includes things like weed trimmers, gas-powered blowers, edger machines, and even ice augers! So, if you are loyal to one specific brand, you might be able to save a little money by buying their in-house two-cycle oil for air cooled engines.
How To Correctly Mix Two-Cycle Oil & Gasoline?
Before the first drop of oil contacts the first gallon of unleaded gasoline, you need to make sure you understand the proper mix ratio for your lawn mower. A lot of lawn mower manufacturers will print the preferred ratio on the lawn mower engine hood, or they will stamp it into the metal near the fuel tank. You should also be able to find it in the owner’s manual if you still have it. You’ll usually see it expressed as something like 50:1 or 24:1.
You might be able to save a little money by buying the big jug of two-cycle oil. Though this requires a fair amount of measuring by eye. If you don’t have a lot of experience mixing two-cycle oil and gas, you might want to look for the pre-measured bottles of two-cycle oil. They cost a little more per fluid ounce but they are pre-measured to be the perfect volume for one gallon of gas.
With these, you just take a gas can, fill it with one gallon of high octane unleaded gasoline, and pour the pre-measured two-cycle oil into the gas can and give it a gentle swish. It’s a good idea to label the gas can with the mix ratio and dedicate it to that specific mix ratio.
If you have a more experienced eye, and a steady hand, you can use the special gauge on the side of a larger two-cycle oil jug to measure out the volume you need. Into one gallon of gas.
It’s worth noting that you should always mix the two-cycle oil into a gallon of gasoline in the gas can. You should never try to mix it directly into the two-stroke lawn mower’s fuel tank. Not only is it very hard to accurately pour, but it’s difficult to mix, which can lead to an inconsistent mix being delivered to the combustion chamber.
What Type Of Oil For A Four Stroke Lawn Mower Engine?
Four-stroke lawn mowers are very similar to the gasoline engine in your car, truck, or van. Most manufacturers engineer them to be compatible with standard SAE 10W 30. Though this isn’t always the case. Some manufacturers will design their four-stroke lawn mower engines to run on different weights of oil or to use a synthetic blend with better viscosity and resistance to thermal breakdown.
If you’re in a pinch and you’re not sure what type of oil your four-stroke lawn mower is designed to use, you can usually get by with SAE 10W 30. Though it’s always a good idea to go with the manufacturer’s recommended oil.
Some Lawn mowers Use SAE 5W 30
As an automotive oil SAW 30 or SAW 10W 30 are better at colder temperatures, which really doesn’t apply to lawn mowers that run at higher temperatures on warm days. You’re rarely ever running your lawn mower when it’s under 40-degrees F outside.
This has spurred a trend in lawn mower manufacturers who are engineering their newer 4-stroke engines to run on SAE 5W 30. While it’s very similar to its 10-weight sibling, 5W 30 tends to deal with warm engine temperatures better. It also tends to do a better job of working itself into the microscopic textures in the cylinder walls. This makes it especially handy for older four-stroke lawn mowers and commercial riding lawn mowers that are ultimately going to put on a lot of operating hours in their life.
How Often Should I Change The Oil In My Lawn Mower?
Most four-stroke lawn mower engines should have their oil changed every 50-hours of operation. For most residential lawn mowers this translates into roughly once a year. It’s a good thing to do when you take the lawn mower out in the spring.
Though there are some newer models with engines where you simply check the oil level after every two or three mowing sessions. Then you merely top them up with fresh oil, and you never need to worry about performing a standard oil change.