What Kind of Gas Does a Dirt Bike Take? (Answered)

Written by

James Stevens

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Robert A. Verdin

what kind of gas does a dirt bike take

There’s a mumbo jumbo of terms to think about in the motocross world. Whether you have a 125cc bike, gas types are confusing, and you don’t want to mess things up and drive up your expenses much higher if things go wrong.

Good thing you’re here because here is a detailed answer to your question–⁠what kind of gas does a dirt bike take?

This typical fuel you fill for any dirt bike is ethanol-free unleaded gas that ranges from an octane rating of 87 to 92. But depending on whether you have a 4-stroke or 2-stroke engine, gasoline mixed with oil or gas with a higher octane rating is considered to avoid complications.

Types of Dirt Bike


1. 4-stroke engine

This dirt bike has a larger engine, and with it comes more flexibility on what type of gas you can put in. The 4-stroke can take mixed gas and still be okay with it, as the performance is still the same.

Most newer 250cc dirt bikes or higher have 4-stroke engines as it is environmentally friendly. But the downside is it is much more expensive and consumes more fuel.

What kind of gas does a 4-stroke dirt bike take?

Thanks to the 4-cycle engines’ newer technology of engine build, you can use unleaded gas with them with almost any octane rating.

Depending on the model of the bike, you can even fill it up with 82-octane gas if your model doesn’t require premium-rated octane gas.

You can even go with ethanol since it’s cheaper and doesn’t contribute to air pollution. When using lower-rated gas, just be wary of an engine “knocking” (discussed later in the article).

2. 2-stroke engine

2-cycle dirt bikes have a smaller engine, giving you a lesser fuel consumption. When it comes to performance, this has better acceleration but is much louder and emits a lot of smoke.

What Kind of Gas Does a 2-stroke Dirt Bike Take?


According to experts, the best gas for 2 stroke dirt bike is 92 or 93-octane, ethanol-free fuel.

Also, the fuel for a 2-stroke engine can be a gas and oil mixture. A lightweight build such as a 2-stroke does not have separate space for oil, and the oil keeps your engine lubricated, making it smoother to function.

In this case, unleaded gas with high ethanol is not allowed for 2-cycle dirt bikes because the presence of ethanol will interfere with the mixture, and the lubrication process for the engine will stop, causing irreversible damage to the engine.

There are two kinds of oil you can use for the mixture:


  • Injection oil – This oil is convenient because you just inject oil and don’t have to worry about the proper ratio of oil and gas since it is predetermined. Another benefit is if you have premium injection oil, you can have less fuel consumption and less smoke.
  • Premix oil – The premix can seem intimidating when you start because it’s a hassle, but it can be the right choice if you want better control over the mix of the gas and the oil.

So, this method can be a safer option for your engine because the risk of damaging your engine is more controlled than the injection oil.

For the right amount of dirt bike gasoline to oil mixture, it’s best to refer to the user manual for recommendations when it comes to this.

Types of Gas


Dirt bikes use unleaded gas for fuel, and considering the octane rating you use is essential. There are extremes such as 82-octane gas or 100-octane gas, but the three common types of octane rating in gas for motorcycles are:

  • 87 (regular)
  • 89 (midgrade)
  • 92 (premium)

This rating is a measure of the steadiness of the combustion of your fuel. The higher the rating of the unleaded gas, the more resistant it is to heat, so it prevents detonation or “knocking” at higher temperatures in your engine.

Detonation refers to when the gas ignites to the pressure and heat exerted in the engine. The more engine knocking you hear in your bike, the less fuel efficiency and performance, and the more problems you have to deal with in the future.

However, prices rise as you go for higher octane ratings, so the only drawback is that it is considerably more expensive in the long run.

What Happens if You Use the Wrong Gas for a Dirt Bike?


The amount of danger will vary depending on what kind of gas you put in. Luckily, there are still things you can do to prevent a disastrous mishap if you realize the mistake you made early on.

Here are some scenarios where you put in the wrong gas and some suggestions of what you can do:

1. You fill low-octane gas for a dirt bike requiring high-octane gas.

The fuel for a 4-stroke dirt bike is flexible, so you’ll be fine. Unless you hear serious engine knocking issues, the only downside is you will have a lower power performance.

If you have a 2-stroke and put a lower octane fuel than the manual recommends, the knocking issue will be much more common.

The smaller engine will not be able to handle the early combustion of the gas, causing severe damage. So do not use the bike and drain out the fuel.

2. You put a different fuel for the dirt bike.


  • Diesel – The intended fuel for dirt bikes is unleaded gas, so accidentally putting diesel on it is extremely dangerous. The motorcycle will emit heavy smoke and cause it to lose engine power.

Once you realize this mistake, park immediately and drain the fuel.

  • Ethanol – This is relatively safe when you go for the recommended amount. Gas for 4-stroke dirt bikes mixed with ethanol is safe, but it is a different story for a 2-cycle as it will dry out the engine, causing complications.

The best option is to avoid high ethanol content if you have the budget to prevent corrosion.

  • Unmixed gas for 2-stroke dirt bikes – Oil keeps your engine lubricated. If you directly pump gas, there will be a high chance of overheating because the wear and tear will damage the engine.

Wrong ratios of gas to oil mixtures can also produce the same problem for engines, especially when there’s less oil. Remember that the most common ratios for most dirt bikes are 40:1 and 32:1.

  • Mixed unleaded and premium gas (87+89, 89+92, 87+92, etc.) – If you have a dirt bike without a specific higher octane rating requirement, this is generally safe but not cost-efficient as it only results in a midgrade quality.

Tips to Know What Kind of Fuel a Dirt Bike Uses


In general, the most important thing to know what fuel you need is to learn what engine your motorcycle uses.

To make things simpler, when you ask yourself, “what gas do motorcycles use,” here are tips you can follow as a rule of thumb when fuelling your bike:

  • 87-octane fuel is called regular fuel for a reason. You can use it with almost any type of dirt bike. So start from there, and go up as preferred.
  • When you hear a “knocking” sound in your engine, you must get higher-octane fuel for your bike.
  • E10 (10% ethanol gas) is popular nowadays as it reduces air pollution, but make sure to avoid anything higher than that because it can cause engine corrosion.
  • Use the recommended gas, not dirt bike race fuel, unless you intend to compete. It makes no real-world difference in performance if you have no modifications for higher engine compression.

What Are the Best Gas Dirt Bikes for Adults?


Dirt bikes for adults should be in the range from 125cc – 250cc for a smooth and exciting ride. Most beginners will go for products by Yamaha and Honda for a good deal.


Indeed, there is no black-or-white option when answering, what kind of gas does a dirt bike take?

There are numerous things to consider, but hopefully, we’ve cleared some of your lingering questions and finally decided on what’s best for your motorcycle.

It is worth knowing all this information about dirt bike fuel to get the optimal performance you strive to achieve. After all, this hobby is what gives us happiness.

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James Stevens

James Stevens is an expert bike mechanic who knows everything from basic repairs to custom modifications. What sets him apart is his ability to explain complex concepts in a way that's easy to understand. Check out his content on Speedway if you need help with upgrades or modifications for your bike.