May 11, 2021 5 min read

If you just got yourself a motocross bike, or even if you’ve had it for a while, one question you surely have asked, or are still asking is what fuel to use on your motocross bike? When you hold the hose to pump gas, you probably ask yourself, am I doing this right? Let’s take some weight off your shoulders.

Any fuel type between 87-octane and the 92-octane will work just fine depending on the type of motocross bike you own. If you own a 4 stroke, for example, the 82-octane works just fine, but for a 2-stroke, you should go for the ethanol-free higher octanes (92 and 93) because the lower octanes tend to detonate. Two-stroke dirt bikes also require a special fuel/oil mix. 

However, it is becoming increasingly rare to find ethanol-free fuel these days because ethanol helps boost the performance of the engines. In this case, your choice of octane shouldn’t contain anything more than 10% ethanol.

Knowing what type of fuel to use in your motocross or dirt bike isn’t all you have to know when you have these engines. Using only the right products and providing proper care for your bike, will go a long way in building their life span exponentially. Now let’s look at a few other key factors about the proper care of dirt bikes.

MX bike num 112 sitting on a Risk Racing ATS adjustable top stand in the grass under a canopy

What is a Motocross Bike?

A motocross bike is a special type of dirt bike, probably the most popular made up of lighter metals relative to the regular motorbikes. Motocross bikes are usually made from aluminum instead of the other heavy metals that are characteristic of regular dirt bikes.

They all have different capacities depending on what they were built for, who is handling them, and the type of tasks they are being used for. They have the ability to go through all sorts of “off roads” such as rocky paths, mountains, mud, you name it.

The word motocross came about as a combination of two words “motorcycle” and “cross country”. The bikes can be bought ready to race or adjusted to suit the owner’s taste. Some people use these bikes to race, others just use them to get through bad roads maybe while farming or hiking.

Risk racings EZ utility jug w fuel near dirt bike on ATS stand and pit mat by RR

Is Ethanol Suitable for Motocross bikes?

Yes, ethanol is suitable for larger dirt bikes like the 4 stroke dirt bike because it improves performance but this is not the same case with the 2 stroke dirt bike, as it will damage its engine. I would always recommend staying away from ethanol as much as you could. It will deteriorate various parts of the bike over time.

Fuel for engines has been created to undergo combustion to a certain level. This combustion is achieved upon compression of the fuel mixture by the internal piston. When this occurs, a spark sets off which provides energy for the engine to run.

The reason ethanol doesn’t work well in 2 stroke bikes is that it causes oil to break down in the fuel/oil mix. Even though all 2 stroke fuels contain ethanol for lubrication and other things, it is always kept at a minimum in order to reduce these effects. Oil breakdown causes long-term damage.

EZ utility jug sitting on tail gate near lock n load gloves n coozie all by Risk Racing

What Happens if You Put Regular Gas in a 2 Stroke Dirt Bike

Running a dirt bike on regular gas instead of 2-cycle oil is a recipe for disaster in the long term. The dirt bike will work after you fill it with regular gas but it is just a matter of how long. Some may take hours before they crash but eventually, they will. 

2 stroke engines require oil for lubrication, in the absence of this, there’ll be so much friction that leads to very serious wear and tear. Regular gas will score the cylinder and piston and then subsequently lose compression until it is unable to run again.

motovan carring multiple ez utility fuel jugs by risk racing and a dirt bike on a hitch mount platform

Can You Run 110-Octane in a Dirt Bike?

110 octane is also known as race fuel. Some people swear by it saying that it makes their bikes go faster. Actually, how much you spend on fuel doesn’t really affect your speed in any way. Of course, there’s no problem if you have the money to spend but if you don’t have room in the budget, then you should consider cutting out these expensive fuels.

Playing with the tire pressure or using fuels high in oxygen can give you a better shot at being the top racer on the podium if you experiment and get everything dialed-in. The 110-octane will for sure produce a nice scent from the exhaust and leave your tank coated with a nice grey color but that is about it.

The use of octane in fuels is to provide a detonation resistance, or resistance to knock. Most engines require the maximum octane level to perform this function to be at 93. What this means is your bike will perform absolutely well at a lower octane level as long as it is able to resist detonation. Fuels with oxygen as an additive will increase the speed of your bike because they are lightweight and boost power.

mx dirt bike number 75 sitting on an ATS motocross stand by Risk Racing on white studio BG

Can I Use E85 in my Dirt Bike

E85 contains 85% of ethanol and 15% gasoline. Using it, therefore, means that you will have to invest more in fuel. However, due to its cheap nature, buying more fuel shouldn’t cost you anything extra than what you typically spend on gas.

Using E85 however means that you will constantly have to rejet your bike, good luck with that. You can experience a 1-2% power boost when you use it, but only if you don’t raise compression to take advantage of the high octane. Worthy of note is the fact that ethanol corrodes aluminum, gaskets, rubber seals, and hoses so you may have to tread with caution.

All of that for 1-2% more horsepower?!... I can get more horsepower than that by slapping new stickers on it! :)

mx bike number 787 sitting on an ATS adjustable top stand by RR near dusk tree and hill background

What Kind of Gas Do You Put in a 2-Stroke Dirt Bike?

2 stroke oils can be put in two categories; injector safe oil, and premix oil. Let’s look at each of them individually and figure out what is going to work best for 2 stroke dirt bikes.

  • Injector Safe Oil

A fuel injector is found in the engine’s fuel delivery system and it functions in receiving and spraying gasoline or diesel into the engine in the form of high-pressure mist. An injector-safe oil, therefore, is one that will not tempter with these functions, oil that does not form clogs.

  • Premix Oil

Premix is a mixture of oil and gasoline. Oil serves as a lubricant and it burns off alongside fuel. Several types of oils exist including the Ester-based synthetic oil. This oil mixes with high-quality gas making it consistent enough to take away your cold-weather worries. 

2 stroke bikes use premix in their engines. The particular type of premix to be used in a 2 stroke dirt bike is not a rule of thumb. To solve this, check your user manual, manufacturers will always leave you with recommendations about what type of premix to use, and in what ratio.

ez 3 or 5 gallon utility jug with hose bender spout by risk racing mounted in the back of a pickup truck

Conclusion

From this explicit write-up, it is clear that there are loads of different fuels available in the market for motocross bikes. Being patient in knowing the contents of these products will help you know which product best matches your need. Be it a 4 stroke or 2 stroke dirt bike, this article has very clear guidelines on how to go about making decisions in both situations. Also, don’t forget to go through your user’s manual to learn more about your bike from the perspective of the manufacturer, they will always know better.


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