Can A Motorcycle Use Car Engine Oil? An Engineer’s Perspective

Lubrication and oil are an extremely important part to any machine, especially motorcycles. Oil isn’t a “one size fits all” and many wonder how interchangeable oil can be between different types of machines. One common question I get from fellow motorcycle riders is if it’s okay to use car engine oil in a motorcycle.

So, can a motorcycle use car engine oil? Using car engine oil in a motorcycle for a brief amount of time is okay, whether this entails using it for an emergency or accidentally putting in this type of oil. However, this should not be done regularly and if car engine oil is put in your motorcycle, it should be changed sooner than regular oil change intervals.

I’m a motorcycle enthusiast, a previous owner of a motorcycle restoration business, and a mechanical engineer that works for an oil company. I have a thorough understanding of how oil works (since I talk about it all day at work) and I have a vast knowledge how how it impacts the functionality of a motorcycle. Keep on reading to hear a simple explanation of why it’s okay to use car engine oil in a motorcycle for a brief amount of time but also why it shouldn’t be common practice.

Why Car Engine Oil Is Okay To Use Temporarily

There have been several instances I’ve heard from family and friends where they’ve accidentally grabbed the wrong bottles of oil either from their garage shelf or the shelf in the store and put it in their motorcycle without realizing what they had done.

Or, some people find themselves in instances that require them to put car engine oil in their motorcycle because an emergency situation called for it. Some type of oil is certainly better than not enough or no oil at at all. You can read my other article here to learn more about what happens when a motorcycle runs out of oil.

Surprisingly, it’s actually okay if you’ve put car engine oil in your motorcycle. There is a difference between car engine oil and motorcycle oil (which we will get in to later), but there are enough similarities that will get your motorcycle lubed up just fine temporarily.

The primary function of engine oil is to protect everything that’s inside. When car engine oil is put in a car and the car is turned on, it is sucked up from the oil reservoir from the oil pump which then delivers the oil through an oil filter to clean the oil. The oil is then delivered through various circuits of oil passageways to critical engine parts such as the bearings, pistons, and the valve train.

Because most of these parts are moving so fast, it vital that the oil provides lubrication to them or else the parts risk heating up and causing so much friction that they ultimately weld together and/or break.

A motorcycle engine works similarly to a car engine. Motorcycles consist of an oil reserve where the oil goes through an oil filter and oil is then delivered to the vital parts of the motorcycle. With a lot of motorcycle engines, the oil also flows through the transmission since the two are essentially one combined unit.

Because of the similarities in their function, using car engine oil in a motorcycle isn’t detrimental to it. However, if it is used too long or used too much, those differences between the two oils can start to take a toll on the motorcycle engine which can eventually lead to bigger problems.

The Difference Between Car Engine Oil And Motorcycle Oil

Though it is okay to temporarily use car engine oil in a motorcycle, it’s not okay to consistently use it. As I mentioned before, there are some differences between the two oils and due to those differences, a motorcycle will start lacking some vital components it needs from the oil and will start breaking down.

Though a car engine and it’s transmission are connected, they each are their own separate entity and require their separate kinds of oils to lubricate the insides. The car’s engine oil cannot be used in the transmission and vice versa.

For most motorcycles, their engine and transmission are also connected but are open to each other, meaning they share the same oil to lubricate the insides. Essentially, motorcycle oil lubricates both the engine and the transmission.

Motorcycle oil has more lubrication properties and other frictional type of additives that the transmission needs to function properly. The biggest difference between car engine oil and motorcycle oil is that car engine oil does not have the extra friction additive and lubrication properties that motorcycle oil has to carry out the functionality the motorcycle transmission needs.

Over time, this will start to have a negative impact on the transmission of the motorcycle.

What Happens If You Use Car Engine Oil Too Often In Your Motorcycle?

Though car engine oil used in a motorcycle is an okay patch up, it should never be used consistently or for long periods of time. There are a lot of risks involved by doing so. I’ve restored dozens of motorcycles and have seen first-hand the impact of using the wrong type of oil.

As we mentioned before, the greatest risk you run is the transmission not getting enough lubrication. The gears in your transmission could ultimately wear down faster from the lack of higher lubrication properties which can cause major transmission issues down the road.

That means you can also have some engine issues as well. When the transmission starts going out and breaks apart due to lack of lubrication, small metal shavings can be created.

Because the transmission and engine are connected in a motorcycle, that same oil also travels through the engine so the engine receives those metal shavings. That in itself can cause catastrophic damage. Because the engine and transmission are one unit on most motorcycles, when one goes out that means the other one is close behind and you may simply need to replace the whole unit.

If you have used car engine oil in your motorcycle, you will need to change your oil and replace it with oil meant for motorcycles as soon as you get a chance. Don’t plan on using car oil for a long period of time in your motorcycle.

The Right Oil To Use In A Motorcycle

Manufacturers usually make it pretty easy for the rest of us to know what oil is supposed to be used for which vehicle. Most motorcycle oils will specifically say on the bottle that it’s meant for a motorcycle so we don’t mistake what kind of oil we’re purchasing.

With that being said, you can’t simply walk into the auto store and grab any oil bottle that has a picture of a motorcycle on it. Each motorcycle requires a certain viscosity of oil that you need to use. You can tell which type of oil your motorcycle needs by either reading the oil cap, reading the owner’s manual, or looking it up online.

Aside from the type of viscosity your motorcycle requires, you should also know the type of oil you need with certain types of additives and materials inside of it; There are three main types.

The first type of motorcycle oil is mineral oil or MO. This is the most basic type of oil and is recommended for smaller capacity motorcycles or motorcycles that don’t have large engines. This is usually the more affordable type of oil and considered more generic

The second type of oil is semi-synthetic oil or SS. This is a mixture between mineral oil and full synthetic oil. This oil is usually used with motorcycles that are still on the smaller capacity scale but are used daily such as your daily commute to work.

The third type of oil is fully synthetic oil or FS. This is a type of oil that is best used for high performance motorcycles with engines that are put under a lot of stress. This may include super bikes or race machines. This is considered the most expensive and highest quality of oil.

Some of these oils are interchangeable with the motorcycle you have, but you’ll need to be careful with how you do that. Using synthetic oil on a smaller capacity motorcycle hardly holds any bad outcomes, while using mineral oil in a high performance motorcycle may cause issues.

Conclusion

To recap, it is okay to temporarily use car engine oil in a motorcycle, especially when there is not other choice. Some type of oil is much better than no oil at all. However, this shouldn’t be used long term and needs to be replaced with the correct oil the motorcycle needs. Otherwise, the transmission (and ultimately the engine) will start to break down.

Have you guys ever used car engine oil in your motorcycle? How did it work out for you? Feel free to comment or reach out for a discussion, we’re happy to hear what you have to say!