Can I use 5W30 In My Lawn Mower? 10W30? 10W40?

ByLRFIX Updated:

Is it time for a lawn mower oil change? Asking yourself: "Can I use 5W30 In My Lawn Mower?" You're in the right place. If you are looking for answers to oil/fuel mix questions, visit the oil mix chart instead.

Short answer: Yes, you can use 5W-30, 10W-30 and 10W-40 oil in your lawn mower. They are common oil grades used in many small engines, including push mowers.

Best answer: To understand which type of oil is best for your lawn mower you'll need to understand what the numbers mean, which I'll describe and compare for you in this oil guide.

For riding mowers, which typically have more powerful small engines, use the manufacturer recommended oil type only.

What do the numbers mean?

When comparing 5W-30, 10W-30 and 10W-40 oils for your lawn mower, the important difference is the oil's viscosity characteristics.

Viscosity is a physical property that describes a fluid's resistance to flow. In simpler terms, it refers to how thick or thin a fluid is and how easily it flows.

A fluid with low viscosity flows more easily and is thinner, while a fluid with high viscosity flows less easily and is thicker.

The "W" in the oil grade stands for winter, indicating how the oil performs in cold temperatures, while the numbers before and after the "W" represent the viscosity at low and high temperatures, respectively.

Can I use 5W30 In My Lawn Mower?

5W-30 in lawn mowers

  • Viscosity at Low Temperatures: 5W-30 is designed to flow well in cold temperatures, making it easier to start your lawn mower in chilly weather.
  • Viscosity at High Temperatures: It also provides sufficient protection at high temperatures, ensuring proper lubrication during hot operating conditions.
  • Suitable for: 5W-30 is suitable for regions with colder climates or for those who mow early in the morning when the temperatures are lower.

10W-30 in lawn mowers

  • Viscosity at Low Temperatures: Like 5W-30, 10W-30 flows well in cold weather, enabling easy starting of your lawn mower in colder conditions.
  • Viscosity at High Temperatures: It maintains a stable viscosity at high temperatures, providing good engine protection during hotter operating conditions.
  • Suitable for: 10W-30 is a versatile oil grade that works well in a wide range of temperatures, making it suitable for most moderate climates.

10W-40 in lawn mowers

  • Viscosity at Low Temperatures: 10W-40 is slightly thicker at low temperatures compared to 5W-30 and 10W-30, which might make cold starting a bit harder in extremely cold conditions.
  • Viscosity at High Temperatures: It maintains its viscosity adequately in hot conditions, offering good protection during high-temperature operation.
  • Suitable for: 10W-40 is ideal for regions with hotter climates or for lawn mowers subjected to heavy use or operating in high-temperature conditions.

SAE 30 in lawn mowers

  • Viscosity at Low Temperatures: SAE 30 is a single-grade oil, meaning it lacks the "W" (winter) designation and may not flow as well in very cold temperatures. Cold starting might be more challenging in colder regions.
  • Viscosity at High Temperatures: It provides adequate protection at high temperatures, suitable for normal lawn mowing conditions in warm climates.
  • Suitable for: SAE 30 is best suited for lawn mowers used in regions with consistently warm temperatures and minimal temperature variations.

Old Gas Powered Lawn Mower

Older lawn mowers and SAE30 oil

You may have noticed that manufacturers of older lawn mowers almost always recommended SAE30 oil be used. While oil technology has improved since then, SAE30 is STILL the best choice for older mowers.

In fact, as your mower ages, you may want to switch to SAE30 as well, and the reason is simple. Worn parts.

As the mower ages friction wears components down gradually. The tolerances in the small engine, for example, will increase slightly, which in turn may allow small amounts of oil to get passed the piston rings.

When that happens you typically start seeing a blue smoke coming from your mower exhaust muffler, especially at startup when the engine is cold.

Multi-viscosity oils, those with a W in their grade, are thinner than SAE30, which retains the same viscosity at all temperatures, and it can leak through the piston rings more easily.

So, as your mower ages, switch from 5W-30 to 10W-30, or better yet to straight SAE 30 oil. This will help prevent the oil from leaking past the cylinder rings and will give your lawn mower's engine a little more life before it needs a rebuild.

I hope that helped you understand the differences between oil grades a bit better, especially when it comes to lawn mower oil. Happy mowing!