Choosing the Right Engine Oil Grade for Your Lawn Mower

No doubt about it, engine oil is important to your lawn mower's life.

In fact, selecting the right oil can prolong the life of your mower engine indefinitely. 

But how do you know which oil to choose?

With so many factors to consider, selecting the best oil grade can seem be overwhelming. 

Well, fret not, we have got you covered. 

Here is what you need to know about selecting the right grade of oil! 

What Is Oil Grading and Why Does It Matter?

The Society of Automotive Engineers (SAE) developed a categorization of motor oils in which the viscosity, or thickness, is measured (0W-30, 5W-30, etc). 

Viscosity is the fluid’s resistance to flow. Thin fluids have a low viscosity, and fluids that are thick have high viscosity. The oil in a lawn mower’s engine changes in viscosity when it is either heated or cooled. By selecting the right engine oil, you can avoid having to troubleshoot lawn mower issues later. 

Understanding Oil Grading: Simplified

So what does SAE-0W-30, 5W-30, or 10W-30 even mean?

Here’s how it works. The higher the initial number, the thicker the oil—0 is like water and 10 is like honey. 

The “W” stands for winter and represents the viscosity of the oil in cold conditions—meaning it has been tested at very low temperatures such as -30° Fahrenheit and can properly lubricate in that environment. 

The number 30 at the end represents how well the oil flows after it has been heated to 212° Fahrenheit or higher. 

Hence 0W-30, 5W-30, and 10W-30 all have the same viscosity at 212° Fahrenheit, but at lower temperatures, 0W-30 has the least viscosity and 10W-30 has the highest viscosity.

Know Your Environment

Look, oil behaves differently at various temperatures. The outdoor environment can help determine the correct oil for any lawn mower engine.

Even though lawn mowing normally occurs during the warmer months, lawn mowers can still be used in the cooler months for leaf mulching and/or removal.

Other equipment, such as snow blowers, will solely be used in the winter months, and will certainly have different oil requirements. 

What oil grade is right for the temperature?

So, how do I know which oil to select based on the weather in my area? 

It’s simple, here is what you need to know: 

• Use SAE 30: in warmer temperatures of 40° F and higher (5° C and higher)

• Use SAE 10W-30: for a varying temperature range between 0 to 100° F (-18 to 38° C); this grade of oil improves cold weather starting but may increase oil consumption at 80° F (27° C) or higher

• Use a synthetic oil SAE 5W-30: for very cold temperatures of -20 to as high as 120° F (-30 to 40° C) providing the best protection at all temperatures as well as improved starting with less oil consumption

• Use SAE 5W-30: for very cold temperatures of 40° F and below (5° C and below)

• For continuous-use: such as commercial lawn cutting or pressure washing, use 15W-50 Oil (temperatures from 20°F to 130°F)

When and How Often Should I Change My Lawn Mower's Oil?

Oil in a lawn mower needs to be changed regularly to ensure its cleanliness and effectiveness. 

It’s simple, most manufacturers recommend changing the oil every 20-50 hours of operation. Part of regular lawn mower maintenance includes changing your engine’s oil.

However, it’s best to refer to the owner’s manual to make the best informed decision. Keeping a log of how many hours the mower has been used will help maintain the proper oil changing regiment.

Pro Tip! Clock how long it takes you to cut the grass once. If it takes you 1 hour, and your manual says to replace the oil every 20 hours. You know that after cutting your lawn 20 times to change the oil. 

Why Is Engine Oil Called the Lifeblood of Your Lawn Mower?

Most people know this, the heart is one of the most important organs in an individual’s body. It acts like a dual-chambered pump that circulates blood and provides the body with oxygen and nutrients it needs to survive. 

Needless to say, blood is just as important as the heart; it brings a steady supply of essential food and oxygen to the body’s cells. And engine oil acts like the blood of your lawn mower.

Your Lawn Mower’s Engine is the Heart of the Machine

When looking at a lawn mower engine, one can think of it as the heart. It provides the power to rotate the blades and turn the wheels. 

The motor oil one puts in the engine is a lawn mower’s lifeblood, which travels through all parts of the engine, lubricating each component so each can perform its designated task. 

Just like the blood that circulates through your body, the cleaner the motor oil is, the better the engine will run. 

Frequently asked questions

Can I mix different grades of oil in my lawn mower?

Oil of different grades should not be mixed, because its viscosity can change and the performance characteristics of the oil may also change. This can ultimately lead to poor lubrication or damage to the engine. Always use the grade of oil recommended by the manufacturer.

What happens if I use the wrong grade of oil in my lawn mower?

The wrong grade of oil can lead to a range of issues, including reduced engine efficiency, increased wear, and in severe cases, engine failure. The wrong oil viscosity may not provide adequate protection at operating temperatures, leading to faster degradation of engine parts.

How do I check the oil level in my lawn mower?

Ensure the mower is on a level surface and follow the manufacturer's instructions. Typically, you'll remove the dipstick, wipe it clean, reinsert it fully, and then remove it again to check the oil level. The oil should be within the marks indicated on the dipstick.

Is it necessary to change the oil if I rarely use my lawn mower?

Yes, even if your mower gets little use, you should change the oil in it every year. Degradation of oil and accumulation of contaminants would affect the engine if not changed annually.

What is the difference between synthetic and conventional oil for lawn mowers?

Synthetic oil is designed to perform better in extreme temperatures and offer superior engine protection and performance over a longer period than conventional oil. It's especially beneficial for challenging conditions or commercial use, although it may come at a higher cost.

Choosing the Right Oil

Regularly changing the oil in any mower is essential to its prolonged life. 

Since the oil is such a vital component of the internal operations, it needs to be treated like the mower’s life depends on it because it actually does. 

When to change the oil, the different types of oil, and the best oil for the mowing environment you are in- are essential to maintaining the heart of your mower.  

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