Can You Mix Motorcycle Oil With Car Oil?


Oil is quite versatile, but can you mix motorcycle oil with car oil? It is a hot and controversial topic in the motoring community. It is not advisable to mix motorcycle oil with car oil, but like everything in life, there is one exception. Read this article to find out the hard and fast rules about using motorcycle engine oil. Knowing the correct answer is essential for proper motorcycle maintenance. 

Why Oil Is Important For Your Motorcycle

Car engine oils were the base of most motorcycle engine oils till 1998. Since then, oil has had many modifications. The technology of both cars and motorcycles has advanced. Before we get to the nitty-gritty about using it, what does motorcycle engine oil do?

  • It is a lubricant that prevents metal to metal contact by lubricating moving parts. 
  • Oil helps to prevent any internal corrosion.
  • It keeps the pistons and transmission cool.
  • It can also suspend any contaminants until the next oil change.

As you can see, oil is the essential blood flowing through the veins of your motorcycle. Like our bodies, if not managed well, the motorcycle will experience difficulties. So, how can you determine the right oil to use?

What Do The Oil Viscosity Numbers Mean

Motorcycle oil temperature gauge
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If you don’t know anything about oil viscosity numbers, have no fear. Viscosity is a reference to the thickness of the oil. So, if the number is low, the oil is thin and flows easier. The higher the number, the heavier the weight or viscosity of the oil.  

The oil’s viscosity is a crucial element. It determines how the oil flows around the engine and the protection of the machine. The science behind it is second to none. The viscosity can affect the flow of the oil and how it lubricates at different temperatures.

As an example, you might have seen 10W-30. What does this mean? Well, the first number is a measurement of the oil’s flow rate at low temperatures, such as -15 to -20 Fahrenheit. W relates to “Winter”. How oil works in very cold temperatures is important for the “cranking speed” of an engine. So this is more relevant for car drivers as motorcyclists don’t tend to go out when it is freezing. 

The second number relates to the viscosity of the oil at a high temperature. This temperature is usually measured at 212 Fahrenheit. If the oil is thicker, it will provide more protection for your motorcycle engine parts. 

You can check your owner’s manual for the correct oil weight for your motorcycle. It is handy to know this, so if you don’t already know it, you should check it out.

Why It Is A Bad Idea To Mix Motorcycle Oil With Car Oil 

A can of motor oil

Cars and motorcycles function in different ways. Also, when it comes to engine oil, it needs to work for different types of scenarios and setups. There are synthetic oils, regular oils, and differing grades. 

Here are the main reasons why mixing motorcycle oil with car oil is a bad idea:


The auto industry is always looking for ways to improve efficiency and the cost of fuel. So they build new car engines to handle only light, thin oils. Because this car oil is so thin, it is necessary to put additives inside the oil. Sometimes 20-25% of the oil consists of additives.

These additives help the oil to function in the real world and enable cars to cover long distances. Oil thins out as it gets hotter, so that is why placing additives inside it is crucial.

Friction Modifiers

Additives in the oil help to reduce friction in cars, to counter all the extra miles that they do. But motorcycle engine oil needs to have different balanced friction characteristics. For example, you must lubricate the wet clutch. If it isn’t lubricated, it might cause slippage as the clutch will not be able to engage. These new oils with friction modifiers might work for cars and small trucks. But it can be dangerous for motorcycles.

Protecting The Motorcycle Engine And Gearbox

Motorcycles use the same oil for the gearbox and the engine. So, the oil a motorcycle uses needs to protect both the gears and the engine components. The oil needs to be formulated with precise technology to handle these specific requirements. 

Motorcycles Breakdown The Oil Viscosity Quicker

Let’s face it; motorcycles work a lot harder than your typical passenger car. When you are letting it rip, you need to have anti-wear and high-pressure additives to assist you. These additives are not present in standard car engine oil. 

Motorcycle engines are hotter than car engines because they are making more power and spinning faster. So using oil made for your motorcycle is only good common sense. 

Motorcycle Oil Standards

The wrong oil can cause many problems for motorcyclists. So much so that in 1998 the Japanese Automotive Standards Organisation (JASO) created two standards for motorcycle oils to help motorcyclists out. The two markings are MA and MB. 

MA is for motorcycles with wet clutches. MB is for motorcycles with automatic transmissions. So, if you have a wet clutch, remember to look out for the MA marking. Also, be wary of using any oils marked with MB, as they will have friction modifiers inside them.

The One Slight Exception To The Rule

As mentioned at the beginning of the article. You should always use the specific motorcycle oil that your motorcycle guide recommends. In extreme situations, and if you had no other choice, car oil could work. But you need to check the following:

  • Only if the label confirms it is not energy conserving. 
  • It is in the right viscosity range for your motorcycle.

Some people have used car oil in their motorcycles with no problems at all. That is why it is such a contested topic. But if you have a wet clutch, it is not worth considering, due to the potential hazards. 

To Avoid The Oil Mixing Problem Altogether

So you don’t have to deal with the mixing dilemma at all. You could get in the habit of checking your oil once a week. Also, invest in a backup container of oil, just in case.

Why It Is Important To Change Your Motorcycle Oil

Close-up of a Harley-Davidson chrome engine
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Off the back of all this, don’t forget that you need to change your motorbike oil regularly. If you never replace your oil, the additive materials inside it will wear out. Also, the more that you use the same oil, it becomes thicker inside the engine. This thickness makes the engine less efficient. This viscous oil makes the motorcycle engine dirtier inside and can cause you other problems.

If you forget to replace the oil, your engine might end up having a major breakdown. You may only realise at the last minute when it fails on you altogether.

In Conclusion

Using the right engine oil for your motorcycle is essential. If you have considered mixing motorcycle oil with car oil, you need to think again. It is also vital to check the owner’s manual for your motorcycle to find the right oil to use. You might be dying to get your wheels out on the road. But before you roar down that motorway, make sure that you use the right oil to protect your pride and joy.

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