We all know the guy that refuses to put anything less than 93 octane fuel in his RZR. He might even spout off some good-sounding reasons why 93 octane is the way to go: it’s cleaner, has less ethanol, and his engine performs better.
Or maybe he does it simply for peace of mind. Better safe than sorry, right?
We’re here to clear up any confusion you or your riding friends might have about octane rating. Namely, should you run premium gas in your UTV or ATV?
The truth is that running anything other than the manufacturer recommended octane fuel is a bad idea. It won’t give you better performance, and it might give you worse performance overall. Here’s why.
Octane itself refers to a hydrocarbon molecule made of eight carbon and 18 hydrogen atoms. It’s a key ingredient in fuel. Ask the next three people you run into what octane-rating you see at the pump is and you’ll hear everything from it being the amount of octane in the fuel to fuel’s ability to burn better.
The octane rating you see when you go to the pump refers to that fuel’s ability to resist igniting and the efficiency of that burn as compared to a baseline hydrocarbon fuel mixture. The specific number you see listed—87, 91, 93—is determined through lab tests.
A fuel with an 87-octane rating has 87% of the efficiency of the baseline mixture. A fuel with a 101-octane rating is 1% more efficient than that baseline. It doesn’t necessarily correlate to the amount of octane in fuel at all. Yeah, that’s a weird definition. Just go with it.
But what does that mean practically in an internal combustion engine like that found in your RZR, Maverick, or any UTV that runs on gasoline? To understand how octane affects your engine, you first need to understand how the pistons in your engine work.
The engine in your UTV is a four-stroke engine which means each piston completes four actions in a cycle to drive the crankshaft. In the first stroke, the piston lowers in the combustion chamber and the chamber fills with a mixture of atomized gasoline and air.
In the second stroke, the piston moves up again compressing the gas and air mixture. This compression causes the mixture to heat up. That way, when the spark plug at the top of the chamber fires, the mixture burns at the perfect time and perfect rate to drive the piston back down. The driven-down piston turns the crank shaft during the third stroke. It’s not exactly an explosion. It’s just a fast, expansive burn similar to the way gunpowder drives a bullet out of the barrel.
And finally, the fourth stroke expels the exhaust and returns the piston to its topmost position so the cycle can start again.
But let’s focus on the second and third stroke right now—that’s where your fuel’s octane rating comes into play. The second stroke is all about the piston’s and combustion chamber’s compression ratio. The compression ratio is determined by the difference in volume when the piston is fully down and when it’s fully up. Most UTVs have a compression ratio between 9:1 and 12:1.
The amount the mixture compresses and the moment the spark plug fires determine the needed octane rating of the fuel. And lower octane fuels are easier to ignite than high octane fuels.
If you use a low 87 octane fuel in a high compression engine, the heat from compression alone will cause it to ignite before the spark plug sparks.
When that happens, you get “detonation” or “knocking,” which is really bad. Knocking drives the piston down early and tries to push the crank in the wrong direction.
At best, you lose power. At worst, you destroy your piston and likely the rest of your engine as well. It’s not good. Most modern machines have knock sensors to counteract this problem, but it’s not a fool-proof solution that can completely prevent damage.
Now let’s talk about the opposite situation: high-octane fuel in a low-compression engine. This is what you see a lot more of when you start asking people about what they run in their UTVs, and it’s not nearly as bad as running an octane below the requirement. It’s still not great, but you shouldn’t end up doing major damage.
When you put 91 or 93 octane fuel in an engine that is built and timed for 87 octane, you end up losing power.
Why?
Again, it’s all about the second and third strokes—the compression and the combustion strokes. Remember, the compression stroke heats the fuel in the compression chamber and the spark plug ignites it. The burning fuel drives the piston down in the combustion stroke delivering power to the machine.
If you use high-octane fuel in a low compression engine, you’ll run into some issues. The compression stroke will heat the high-octane fuel, but not as much as it needs to. That means that when the spark plug fires, it won’t burn as fast as it should. It will still push the piston down, but not with as much force as it’s supposed to. At best, it means less power. At worst, you’ll have some extra soot in your cylinder.
By now you know it’s always best to use the fuel that’s recommended by the manufacturer for your engine. That’s why we’ve gathered up the fuel requirements listed in the owner’s manuals for Polaris and Can-Am models that you folks ask about most.
| Polaris Model: | Required Fuel Type: |
|---|---|
| Polaris Sportsman | 87 octane |
| Polaris Ranger | 87 octane |
| Polaris RZR (non-turbo) | 87 octane |
| Polaris RZR Turbo | 91 octane |
| Polaris RZR Pro | 91 octane |
| Polaris General | 87 octane |
| Polaris Scrambler | 81 octane |
| Can-Am Model: | Required Fuel Type: |
|---|---|
| Can-Am Outlander | 1000R engines: 91 octane All other models: 87 octane |
| Can-Am Defender | 87 octane |
| Can-Am Maverick | 91 octane |
| Can-Am Maverick X3 | 91 octane |
| Can-Am Maverick Trail and Sport | 1000R engines: 91 octane All other models: 87 octane |
| Can-Am Commander | 2020+: 91 octane 1000R engines: 91 octane All other models: 87 octane |
| Can-Am Renegade | 1000R engines: 91 octane All other models: 87 octane |
If you want to know if you should run premium gas in your ATV or UTV and we didn’t list it above, the answer is always in your owner’s manual, which you can find here:
Hopefully we’ve busted some misconceptions for you and now you know if you should run premium gas in your UTV or save a few bucks with standard. Next time you’re out on a ride with your friends and the conversation turns to what octane everybody’s running, don’t stick your nose up in the air and say “well actually…” Instead, just challenge the guy who only runs 93 octane in his stock machine to a drag race. They’ll see really quick what their extra $10 in the tank gets them.
2 Comments
Good article.
My 19 BRP Commander 1000 requires 91 octane as per the manual and the fuel cap. FYI. It’s not just the Mavericks…
Car are truly great! It’s the best machine.