Author: CornishScoots

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When it comes to motorcycle maintenance, one of the most misunderstood – but absolutely crucial – topics is engine oil. Specifically, multigrade oil, like the popular 10W-40, plays a huge role in protecting your engine, gearbox, and even your clutch.

From Monograde to Multigrade: A Quick History

In the early days, engine oils were monogrades, like SAE 30 or SAE 50. These oils worked well – as long as the temperature didn’t change. In cold weather, they got too thick to flow. In hot conditions, they thinned out too much to protect your engine. Riders often had to switch oils with the seasons. Not ideal.

That changed in 1953, when Motul introduced the world’s first commercially available multigrade oil – a game changer. These modern oils use viscosity index improvers, additives that help oil adapt to temperature changes, providing reliable performance in both cold starts and high-heat riding conditions.

What Does 10W-40 Actually Mean?

Take 10W-40 as an example:

• The “10W” tells you how the oil flows at cold temperatures (W = Winter).
• The “40” indicates how it behaves at high operating temperatures (around 100°C).

This means your bike gets smooth, easy startups in the cold and dependable protection when the engine’s running hot – perfect for everything from early morning commutes to full-throttle track days.

What Makes Motorcycle Oil Different?

Unlike cars, most motorcycles use the same oil to lubricate the engine, gearbox, and wet clutch. That’s a lot to ask from one fluid, which is why motorcycle oils contain a carefully engineered mix of:

• Anti-wear agents
• Detergents and dispersants (to keep things clean)
• Anti-foam additives
• Oxidation and corrosion inhibitors
• And specific friction modifiers for smooth clutch operation

Using car oil in your bike might seem harmless, but it can lead to clutch slippage, gear wear, and other headaches. Always choose an oil that’s formulated specifically for motorcycles.

Performance Tip: Thinner Oils in Racing

In high-performance or racing applications, engineers often opt for thinner oils to reduce internal drag and squeeze out every last bit of horsepower. For example, Honda’s legendary HRC Fireblade race bikes run Motul 0W-30, gaining an estimated 3–4 bhp thanks to reduced resistance.

Final Word: Follow Your Manual

Your best bet? Stick to the oil grade recommended by your motorcycle manufacturer. It’s the simplest way to ensure long engine life, smooth gear shifts, and trouble-free riding.

Looking for high-quality motorcycle oil? Check out our selection of Motul, Liqui Moly, and other top brands – specially formulated for today’s high-performance machines. Visit our Shop to view our extensive range of motorcycle oils and fluids.

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