Is it Safe to Switch Between 10W30 and 10W40 Engine Oils?

10W30 and 10W40 oils are probably the most common motor motorcycle oils in the world, and they’re really similar when it comes down to it. 

10W-30 vs 10W-40 engine oils

But how are they different? Can you use 10W30 and 10W40 oil in your motorcycle? Here’s a quick guide to the variations between 10W-30 and 10W-40 engine oils. 

Buy 10W-30 motorcycle oil

Buy 10W-40 motorcycle oil

What Is the Difference Between 10W30 and 10W40 Oil?

Let’s start with what those numbers actually mean. Both 10W30 and 10W40 are multigrade engine oils, which means they carry different weight properties depending on the conditions. 

10W30 motorcycle engine oil

The first grade is the number before the “W”; the second grade is the number after the “W.” Both of these oils are “10W,” meaning that in low temperatures — the “W” stands for winter — they’ll behave as a regular 10W SAE-grade oil. This means the oil is thinner and flows quickly even when cold to lubricate an engine started on a cold day.

The second number, the one after the “W,” is where the slight difference is found in these oils. This second number represents the oil’s viscosity at temperatures above 212° Fahrenheit or 100° Celsius. The higher the number, the thicker the oil is at higher operating temperatures. So the 10W40 oil is slightly thicker than the 10W30 oil when the engine is hot, meaning it offers a little more protection.

10W40 motorcycle engine oil

Think of it this way: both oil grades are good for cold starts. But if you’re in a warmer climate or the engine runs a little hotter, 10W40 is the way to go. If you live someplace colder or the engine runs cooler, the 10W30 works better since it runs a little thinner in cooler temperatures.

Do Different Motorcycle Oils Impact Fuel Economy?

The flow of oil adds drag inside an engine. A thinner oil produces less drag and allows an increase in fuel economy. So a 10W30 oil offers better fuel economy than the 10W40 oil. But choosing an oil based on whether it provides better fuel economy is a mistake. It’s better to choose the oil based on the engine’s operating conditions. 

Can I Use Both 10W30 and 10W40 Oil in My Motorcycle?

Yes you can, but it’s best to use the oil recommended by your motorcycle’s manufacturer for its operating conditions. There is one additional consideration though, and that’s how the oil is related to the clutch

10W30 vs 10W40 oil clutch

Most motorcycles use the same oil to lubricate the engine, the clutch and the gearbox. This is why automotive oils aren’t recommended for use in motorcycles. Car oils have friction modifiers that impact the engagement of a motorcycle’s clutch. So using automotive oil in a motorcycle is an unnecessary gamble.

When it comes to 10W40 vs 10W30 in a motorcycle, either grade will work, but choose a variant that protects the clutch. 

In the end, either 10W30 or 10W40 would probably be fine in moderate climates and conditions. But the higher the heat, the more you might want to lean toward a 10W40 oil.



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