What Kind of Gas Do ATVs Use?

You hit the starter button. The engine cranks, spits once, and then… silence. The battery is strong, the spark plug is new, but the machine won’t fire. That silence on a Saturday morning is the sound of your weekend plans evaporating.

It’s not bad luck. It’s bad chemistry. Gas is the cheapest mechanic you will ever hire, yet most riders ruin their carburetors and fuel pumps to save two dollars at the pump. Understanding what goes into your tank is the difference between riding all day and spending four hours tearing down a carburetor on the tailgate of your truck.

What Kind of Gas Do ATVs Use? Most utility ATVs (Honda Rancher, Polaris Sportsman) run perfectly on 87 Octane Regular unleaded. High-performance sport quads and turbocharged Side-by-Sides (RZR Turbo, Raptor 700) require 91+ Octane to prevent engine damage. However, the most important factor isn’t the octane—it’s the ethanol content. Whenever possible, run Ethanol-Free (Rec-90) gas to prevent water absorption and fuel system corrosion.

The Octane Number and What Your Engine Actually Needs

There is a myth that “Premium” gas gives you more power. It doesn’t. Octane is not a measure of power; it is a measure of resistance to detonation.

Understanding the Anti-Knock Index (AKI)

When you see 87, 89, or 93 at the pump, that is the AKI. It tells you how much pressure the fuel can withstand before it explodes on its own.
In an engine, you want the spark plug to ignite the fuel. If the engine compression is too high and the fuel octane is too low, the heat and pressure will cause the fuel to explode before the spark plug fires. This is called pre-detonation, “pinging,” or “knocking.”
It sounds like marbles rattling around in a tin can. If you hear that sound under load, your piston is effectively being hammered to death.

High-Compression vs. Low-Compression

• Utility Quads (The 87 Crowd): Machines like the Honda Foreman, Yamaha Kodiak, or Can-Am Outlander 500 have lower compression ratios. They are designed to run on 87 Octane. Putting 93 Octane in a Honda Recon doesn’t make it faster. It just drains your wallet. The engine cannot squeeze the fuel hard enough to take advantage of the higher resistance.
• Sport & Turbo Machines (The 91+ Crowd): If you ride a Yamaha YFZ450R, a Raptor 700, or any turbocharged SxS, you are dealing with high compression and high heat. You must use 91 Octane or higher. If you run 87 in a turbo RZR, the ECU might pull timing to save the engine, killing your horsepower, or worse—you’ll blow a hole in a piston.

Manufacturer Fuel Requirements Table

Machine Type	Example Model	Minimum Octane (AKI)	Preferred Fuel Type	Why?
Utility ATV	Honda Rancher 420	87	87 Ethanol-Free	Low compression engine, prioritizes reliability.
Sport Quad	Yamaha YFZ450R	91+	93 Pump or Race Gas	High compression piston requires knock resistance.
Turbo SxS	Polaris RZR Turbo R	91+	93 Pump	Boost pressure increases cylinder heat/pressure drastically.
2-Stroke	Yamaha Banshee 350	91+	93 Ethanol-Free	Highly sensitive to detonation and oil separation.

The Real Enemy Is Ethanol (E10)

The octane rating matters for the engine while it’s running. But the ethanol content matters for the engine while it sits in your garage. And let’s be honest—most of our machines sit more than they ride.

The “Sponge Effect” of Hygroscopic Fuel

Most pump gas in the US is E10 (10% Ethanol). Ethanol is alcohol made from corn. Alcohol is hygroscopic, meaning it attracts and absorbs water from the atmosphere.
Modern cars have sealed fuel systems. Your ATV does not. Look at your gas cap. It has a vent hose. Your fuel tank is constantly breathing in outside air.

Living in Florida, the humidity is 90% almost every morning. I’ve seen brand new gas go bad in three weeks. The vent hose sucks in that humid air, the ethanol grabs the moisture, and suddenly you have water in your tank without ever riding through a creek.

Phase Separation: The Silent Killer

When E10 gas absorbs enough water, it reaches a saturation point. The bond breaks. The ethanol and water mixture separates from the gasoline and sinks to the bottom of the tank. This is called phase separation.
Here is the problem: Your fuel pickup is at the bottom of the tank.
When you hit the starter, you aren’t sucking in gasoline. You are sucking in a slurry of water and alcohol.

• The Result: The engine won’t fire. If it does fire, it runs lean and hot because alcohol burns differently than gas.
• Hydro-lock: In extreme cases, if enough pure water enters the cylinder, the piston comes up and hits a liquid barrier. Liquid doesn’t compress. Rods bend. Game over.

Varnish and Gumming

Even if you don’t get water, ethanol acts as a solvent. It attacks older rubber fuel lines and O-rings. As the fuel evaporates in a carburetor float bowl, it leaves behind a sticky green or brown residue called varnish. This goo clogs the pilot jet (the tiny hole that controls idle).
If your bike starts with the choke on but dies the second you turn the choke off, your pilot jet is gummed up. That’s the ethanol tax.

2-Strokes and Corn Juice Are A Volatile Mix

If you are keeping the legend alive by riding a 2-stroke (like a KX250 converted for woods or a Banshee), you need to be paranoid about your fuel.

Oil Suspension Failure

In a 2-stroke, you mix oil with the gas to lubricate the piston. Ethanol hates 2-stroke oil.
If you let E10 premix sit, the ethanol (carrying water) can separate from the gasoline and the oil. The oil might stay suspended in the gas layer, or settle differently.
When you start that bike, you might be burning fuel with zero lubrication. This leads to scuffing on the cylinder walls and eventual seizure.

• Robert’s Rule: Never leave premix in a plastic can for more than 30 days. If in doubt, pour it in the weed whacker and mix a fresh batch for the bike.

Fuel Stabilizers and Storage Tips

Since we can’t always find Ethanol-Free gas (Rec-90), we have to manage the junk we are forced to buy.

The 30-Day Rule

If you buy E10 pump gas, treat it like milk. It has an expiration date.

• Untreated E10: Starts degrading in 30 days.
• Stabilized E10: Can last 6 to 12 months.

Choosing the Right Additive

Don’t just buy the cheapest red bottle. Look for stabilizers that specifically claim to handle water or ethanol.
I use marine-grade stabilizers (like Sta-Bil 360 Marine or Star Tron). Why? Because boats live in water. Marine additives are chemically engineered to fight hygroscopic absorption more aggressively than standard lawn mower additives.

• Detergents: Also look for “Top Tier” fuel or additives with detergents (like Techron). These help clean carbon deposits off intake valves, which is helpful for older engines.

To Drain or Not To Drain?

This depends on where you live.

• The Florida Method (Humid Climates): Keep the tank 100% full with stabilized gas. If the tank is full, there is no room for air. No air means no condensation forming on the inside walls of the tank.
• The Ohio Method (Freezing Climates): If the bike is sitting for 4 months of snow, drain the carburetor float bowl. There is a small screw at the bottom of the carb. Turn off the petcock, open the drain screw, and catch the gas in a rag. If you leave gas in that tiny bowl over winter, it will varnish the jets.

Troubleshooting Signs of Bad Gas

How do you know if your tank is poisoned? The bike usually tells you.

1. The “Rotten Egg” Smell: Open the cap. If it smells sour, like varnish or turpentine, the gas is dead. Don’t try to run it. Drain it.
2. Hard Starting: The engine cranks forever but won’t catch. This suggests the volatile compounds in the fuel have evaporated, leaving behind the heavier sludge that doesn’t ignite easily.
3. The Sputter: It idles fine (maybe), but when you crack the throttle, it bogs down or dies. This means the main jet is partially clogged with varnish, starving the engine of fuel under load.

Conclusion

Your ATV is a machine of freedom, but it is bound by the laws of chemistry. You can spend thousands on suspension and tires, but if you feed the engine garbage, it becomes a 600-pound paperweight.

Check your owner’s manual for the octane number, but listen to the mechanics regarding ethanol. If you have a local station that sells “Recreational Fuel” (Rec-90), use it. It costs a dollar more per gallon. But a carburetor rebuild kit costs $40 and three hours of your Saturday. You do the math.

FAQ