Can I Use a 10W-40 Car Oil for a 4-stroke Motorcycle?

Yup, it's an FAQ. Will car oil work in a motorcycle? Well yes, it will, but with some caveats. Cars and motorcycles use engine oil and filters the same way, for the same reasons. However ... 

Both engine oil types lubricate and cool the engine, as well as prevent corrosion and isolate particulates that float around the motor. However, car oil needs to last longer and handle more miles. It often has some extra goodies in it to reduce engine friction, and those additives can reduce the performance of the wet clutch system on a motorcycle, which basically swims in engine oil.

How are Motorcycle and Car Oils Different?

The differences between motorcycle and automobile engine oil are many, but the most notable difference between the two is the weight. 

As the automotive industry relentlessly pursues better fuel economy, they’ve lightened up the oil used for their engines. Lighter, thinner oils break down quicker, so the manufacturers have come up with all kinds of additives to offset the breakdown of the oil.

On the other hand, mileage isn’t as much of a concern in the motorcycle industry. So while a car might take a thinner 20 viscosity oil, a motorcycle would take a 40 viscosity. The thinner oil is great in a car where the lower viscosity reduces friction, but that doesn’t work well in a motorcycle's wet clutch system.

Can You Put Car Oil in a Motorcycle?

Yes, it’ll work in a pinch. But here’s one key: make sure the car oil you use isn’t “energy conserving” or some other special type on the label. That’s a sure sign it has additives that will impact your motorcycle’s clutch. 

But really, it’s best to just get motorcycle engine oil, the type recommended by your bike’s manufacturer. Sure, motorcycle oil is a little pricier than car oil, but you won’t use as much of it, and it’ll last longer.