Which oil should I use for my lawn mower - featured

Which Oil Should I Use for my Lawn Mower?

For many homeowners, 10W-40 engine oil is the go-to option when it comes time to change the oil in their lawn mower. As a medium viscosity engine oil, 10W-40 usually works just fine and is suitable for most mowing conditions. Of course, just because something works doesn’t mean that it’s operating at a peak performance level! Keep reading as we answer some popular questions we’ve seen passed around, such as:

  • Is conventional or synthetic oil better?
  • Should I change oils depending on the season?
  • Can I use automotive oil in my lawn mower?

Fortunately, picking out the best oil for your mower doesn’t have to be challenging, and with a little know-how, it won’t be! Since Kawasaki engines are fairly popular across a wide variety of lawn mower brands, let’s begin our journey with a quick look at their recommendations.

The Best Oil for Lawn Mowers With Kawasaki Engines 

Which oil should I use for my lawn mower - man pouring engine oil

As previously mentioned, 10W-40 is a popular choice: even Kawasaki themselves recommend it in certain situations! However, depending on the operating conditions, Kawasaki suggests using different oils. For sub-zero temperatures, SAE 5W-20 is the company’s recommended oil. From the low temperature of -10° F to a high of 86° F, 10W-30 works well.

Similar to 10W-30, 10W-40 also works in temperatures as low as -10° F, but is effective in temperatures up to 104° F! For even hotter climates, SAE 20W-50 offers peak performance, reliably lubricating your engine in temperatures in excess of 110° F. However, those who live in a climate where temperatures stay between 50° to 90° F may also use SAE 30 engine oil as well.

Although many consumers still prefer to use conventional motor oil, it’s also possible to use synthetic oil in a Kawaski mower engine. Synthetic oil handles higher temperatures better, whereas conventional motor oil will begin to break down after 240°F. Naturally, synthetic oil is more expensive than conventional motor oil, but the tradeoff is a longer waiting period between oil changes. However, if the mower you’re using isn’t running a Kawasaki engine, then you should check the owner’s manual before making the switch. 

As you can see, there really isn’t any single “best oil” you should use for your Kawasaki engine. Ultimately, the optimal choice is dependent upon your operating conditions (i.e.ambient air temperature). This means that while one oil might be suitable for summer, you may need to switch come wintertime. While all of these oils will likely heat up far past 100° F inside the motor, it’s the external temperature that will have the most noticeable effect on the performance and longevity of your engine.

Using oil in conditions below its recommended operating temperatures can make it harder for your engine to start up; using it above can damage your motor! By choosing an engine oil that’s matched to your operating conditions, you’ll be optimizing your engine for long-term use and high performance.

FAQ

Can I Use 10W40 Oil in My Lawn Mower? 

Yes, you certainly can! As mentioned above, 10W-40 is suitable for most operating conditions. However, you may find yourself wondering if your automobile’s engine oil will work for your lawn mower engine. Does using mower-specific oil really matter? Well, yes and no.

Let’s begin with the negatives. When using automotive 10W-40 oil you may notice that your oil contains additives, which ultimately results in a slightly diluted oil. For a water-cooled car, this doesn’t pose much of a threat, but for an air-cooled mower engine, this dilution could potentially become an issue over time. Generally, you should stay away from using 10W-40 oil with additives unless specifically recommended by the manufacturer.

That said, most people using 10W-40 won’t encounter any issues during routine usage. Many mowers use 10W-40 for years without ever suffering oil-related failures, and your machine will likely enjoy the same fate. However, we would caution you against relying solely on 10W-40 for your mower. Instead, measure the ambient operating temperatures and make sure your choice of oil matches the recommended oil before use.

Can You Use 2 Cycle Oil in a Lawn Mower? 

That depends: is your lawn mower a two-stroke or four-stroke engine? Most modern lawn mowers use four-stroke engines, which hold the fuel and oil in separate compartments. Unlike a four-stroke engine, two-stroke (2 cycles) engines hold both the fuel and the oil in the same compartment: they are mixed before use. The thicker oil used in four-stroke engines would likely clog up these engines in a matter of time, so instead, they use lightweight two-stroke specific engine oils instead. 

When it comes to four-stroke engines, adding oil in with the fuel is a bad idea. In fact, doing so will quickly cause the motor to overheat! Similarly, when two-cycle oil is used (even unmixed) in a four-stroke engine, you will notice a decrease in performance and perhaps even some smoke.

This is because the two-stroke oil lacks the proper viscosity for the lubrication it’s been tasked with. Although some claim to have used two-stroke oil for short periods of time without damaging the motor, we would recommend avoiding it. Surely, an extra trip down to the store is better than dealing with a seized motor!

Can I Use 5W30 Instead of 10W30 in My Lawn Mower? 

Yes, you can, but should you? Really, it depends on how harsh you’re expecting the winter to be. Although most people are unlikely to be out mowing their lawns in sub-freezing temperatures, for some this might be reality. If you fit into this small segment of people then choosing 5W30 might be a reasonable option. However, both of these engine oils will operate in this temperature range, so why choose one over the other?

As you’ve probably noticed, the first number differs between these oils while the latter stays the same. A lower number is better than a higher number in this case since it means that the engine will start easier in colder weather. Essentially, either 5W30 or 10W30 will work in/above freezing temperatures, but we’d recommend 5W30 if you’re planning on routinely mowing in colder weather.

Wrapping It Up

We hope this post answers the question, “Which oil should I use for my lawn mower?” Remember, the best choice depends on the operating conditions. Use the guide above to help you pick an engine oil based on the temperature. When in doubt, always refer to your engine's operator manual for which oil to use and other maintenance advice.

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