E10, the 10% ethanol gas at most U.S. pumps, is what most small engines are built to handle, and it will run your go-kart, mini bike or ATV fine if you use it fresh. The trouble starts with E15 and higher blends, and with fuel that sits. Ethanol pulls moisture out of the air, and an engine that idles in the garage for weeks gives that moisture time to do its damage. Here is how to fuel, store and troubleshoot so your machine is ready when the weather turns.
TL;DR
- E10 (up to 10% ethanol) is the ceiling for small engines. E15 and higher are not approved for non-road engines like those in go-karts, mini bikes and dirt bikes.
- The real enemy is storage: ethanol attracts water, and gasoline can start to degrade in as little as 30 days.
- Ethanol-free, 87 octane or higher gas is the best choice. If you can’t find it, use fresh E10 with an alcohol-free stabilizer.
- Stabilize before you park the machine, then run the engine a couple of minutes so treated fuel reaches the carburetor.
- A rough start after your first tank of E10 is often old varnish being dissolved, and a fuel filter change can fix it.
Table of Contents
- Why ethanol matters more in a small engine than in your car
- What ethanol actually does inside the fuel system
- E10, E15 and what the EPA says
- Two-stroke engines need extra care
- The best fuel for your go-kart, mini bike or ATV
- How to store your machine without fuel problems
- Signs ethanol is causing trouble
- Our perspective: fuel is the cheapest part of the hobby
- Ready for your next ride?
- FAQ
- Sources
Why ethanol matters more in a small engine than in your car
Your pickup has sensors and a computer that adjust fuel and air on the fly. The engine on a go-kart or mini bike usually doesn’t. Oklahoma State University Extension describes the typical small non-road engine as air-cooled, single or twin cylinder, mostly carbureted and with minimal emissions controls. That means the engine can’t compensate when the fuel chemistry changes.
Use is the other half of it. A daily driver burns through a tank in a week. A kid’s go-kart might run on a Saturday and then sit for a month. Kansas State University’s extension publication on ethanol and small non-road engines points out that many small engines are used seasonally or sporadically, with long gaps between runs. Those gaps are where ethanol does its harm.
So the honest answer to “is ethanol bad for small engines?” is: not on the day you fill up, but potentially over the weeks that follow.
What ethanol actually does inside the fuel system
There are three behaviors worth knowing.
It attracts water
Ethanol is hygroscopic, meaning it absorbs moisture from the air. Briggs & Stratton’s fuel guidance notes that fuel can begin to deteriorate in as little as 30 days, leading to gumming and varnish. Add moisture to that and you get corrosion on metal parts in the tank and carburetor.
It acts as a solvent
Ethanol can loosen deposits in an older fuel system. Those deposits then travel downstream and can clog carburetor jets and filters. Rubber and plastic parts such as hoses and gaskets are the other concern, which is why long-term reliability is better served by alcohol-free fuel. Briggs & Stratton’s experts make a useful distinction: an engine that tolerates E10 isn’t the same as one that thrives on it.
It can separate from the gasoline
Phase separation happens when an ethanol blend picks up enough water that the ethanol and water drop out of the gasoline and sink to the bottom of the tank. The Kansas State publication explains that this water-rich layer sits low, right where the fuel pickup draws from, so the engine suddenly runs rough or stalls. Its figure for a 10% blend is that it takes only around half a percent of water to trigger this. That is a tiny amount, and a half-full tank in a humid garage can reach it.
E10, E15 and what the EPA says
Pump labels confuse a lot of riders, so here is the plain version.
| Fuel | Ethanol content | Small engines (go-karts, mini bikes, ATVs, dirt bikes) |
|---|---|---|
| Ethanol-free (E0) | 0% | Best choice, especially for storage |
| E10 | Up to 10% | Generally acceptable if fresh and stabilized |
| E15 | Up to 15% | Not approved for non-road engines |
| E85 | 51% to 83% | Never |
The EPA’s misfueling rule explains that its partial waivers allowing E15 apply to model year 2001 and newer light-duty vehicles. Engines in powersports and lawn equipment are not covered. E15 pumps are required to carry a label warning consumers about this, under regulations finalized in 2011. If the handle says E15, leave it for the car.
Many riders assume that if E10 works, a bit more ethanol won’t hurt. The U.S. Department of Energy’s study of intermediate ethanol blends tested small non-road engines and found that open-loop engines (the carbureted kind) run leaner as ethanol content goes up. A leaner mixture means a hotter engine. Hotter engines wear faster.
Check your owner’s manual too. Manufacturers set their own fuel limits, and running a blend they don’t allow can put your warranty at risk. Our guide to 87 octane and E10 for mini bikes, including storage and warranty rules goes deeper on that side.
Two-stroke engines need extra care
If your machine is a 2-stroke, such as a 49cc mini chopper, you are mixing oil into the gas yourself, and fuel quality matters even more. NC State Extension has a publication on ethanol and two-stroke cycle engines that covers how an alternative fuel affects these designs. Stale, water-laden fuel in a two-stroke also means poor lubrication, and that is a problem you want to avoid. If you are choosing between engine types, our two-stroke vs four-stroke buyer’s guide lays out the trade-offs.
The best fuel for your go-kart, mini bike or ATV
Here is the order we recommend, based on what engine makers advise.
- Fresh, ethanol-free gas at 87 octane or higher. Briggs & Stratton’s fuel selection advice calls for clean, fresh, unleaded gasoline, and ethanol-free is the ideal.
- Canned ethanol-free fuel for machines that run rarely. It costs more per ounce, but a kid’s kart that burns a quart or two a month doesn’t need much, and it won’t go bad in the can the way pump gas does.
- Fresh E10 with an alcohol-free stabilizer when ethanol-free isn’t available nearby.
Two habits matter as much as the fuel itself. Buy only what you will use in about a month, and use a clean, approved container with a tight cap so moisture stays out. Pure-ethanol-free gas can be hard to find in some areas, so plan a regular stop at a station that carries it, or keep a few cans of the premixed boutique fuel on the shelf.
How to store your machine without fuel problems
Storage is where most ethanol trouble begins, and it’s very preventable. Briggs & Stratton’s storage instructions call for adding an alcohol-free fuel stabilizer and ethanol treatment to fresh fuel, then running the engine for a few minutes so the stabilized fuel circulates through the system. Here is how that looks for a kart or mini bike:
- Buy fresh fuel. Don’t stabilize gas that is already old.
- Add an alcohol-free stabilizer to the fuel, following the package directions.
- Fill the tank completely. Less air in the tank means less room for moisture to condense.
- Run the engine for two to a few minutes, so treated fuel reaches the carburetor.
- Shut it off, close the fuel valve if your model has one, and store the machine somewhere dry.
Stabilizers are the standard industry recommendation for keeping fuel fresh for up to 12 to 24 months, according to the Briggs & Stratton guidance above. For a closer look at choosing one, see our article on which fuel stabilizer protects powersports engines for 30 days or more.
If you would rather not leave fuel in the system at all, draining the tank and running the carburetor dry is an option, but the stabilizer-plus-full-tank method is the one engine makers highlight for protecting against moisture.
Signs ethanol is causing trouble
Watch for these:
- Hard starting after the machine has sat
- Stalling or surging at idle
- Sputtering under throttle
- A sour, varnish smell from the fuel
- Visible water or a cloudy layer at the bottom of the fuel when you drain a sample
- Crusty white or green corrosion around the carburetor bowl
The first step is simple. Drain the old fuel responsibly, refill with fresh gas and stabilizer, and try again. If the carburetor is gummed up, it may need cleaning. Our step-by-step go-kart troubleshooting guide walks through the checks in order.
What if the problems start after switching to E10?
Don’t panic. The Kansas State publication notes that poor performance, stalling or hard starting after first using an ethanol blend is often the solvent action of ethanol loosening old varnish. Often the engine simply cleans itself out, and a fuel filter change is frequently enough to get you running again. If a problem persists after a new filter and fresh fuel, have the carburetor cleaned or rebuilt.
Our perspective: fuel is the cheapest part of the hobby
We talk with riders and parents every week, and the pattern is consistent. Almost nobody loses a good engine to one bad tank. They lose weeks of fun to a machine that sat all winter on half a tank of pump gas, and then wouldn’t start on the first warm Saturday of spring.
Our view is simple. A kid’s go-kart and a mini bike are built to be affordable, reliable fun, and the best way to keep them that way is a fuel routine you can actually stick to. Pick a fuel, stabilize it, use it up or treat it before parking the machine, and keep your owner’s manual handy for the exact fuel limits. None of this is expensive. It takes ten minutes at the end of the season.
And when you are shopping, think about how often you will ride. A machine that will be ridden every weekend deals with ethanol far better than one that comes out twice a year. If it will sit often, plan on canned fuel or a stabilizer habit from day one. If you would rather skip carburetors and fuel storage altogether, an electric kart is a legitimate option, and we sell those too.
— Mario
Ready for your next ride?
Whether you are looking for a first kart for an 8-year-old or a trail-ready machine for the whole family, we carry go-karts, mini bikes, dirt bikes, ATVs and UTVs, plus parts and accessories, all online at GoKarts USA®. If you need a spare tank for a dirt bike, you can find the dirt bike gas tank in our parts selection. Prefer to skip gas entirely? Take a look at the Sport Kart Kids Electric Go Kart, or the Sport Kart Kids Gas Go Kart, a 2.5hp 4-stroke for ages 8 and up if you want a classic gas-powered first kart.
FAQ
Is ethanol bad for small engines?
E10 is generally tolerated by modern small engines, but it isn’t ideal for long-term reliability. The risk comes from ethanol absorbing moisture while fuel sits, which can cause corrosion, gum and phase separation. Use fresh fuel, ideally ethanol-free, and stabilize anything that will sit.
Can I use E15 in my go-kart, mini bike or ATV?
No. EPA’s E15 waivers cover model year 2001 and newer light-duty vehicles, not non-road engines. Higher ethanol also makes carbureted engines run leaner and hotter, which speeds up wear.
How long can gas sit in a small engine?
Gasoline can begin to degrade in as little as 30 days, and ethanol blends are more prone to moisture problems. With an alcohol-free stabilizer, Briggs & Stratton says fuel can stay fresh for much longer, up to 12 to 24 months for the industry-standard products. Even so, check your owner’s manual and run the engine after adding it.
Do I need an additive if I use E10?
Yes, if the machine will sit for more than a few weeks. Choose an alcohol-free stabilizer and ethanol treatment, add it to fresh fuel, and run the engine for a few minutes so it reaches the carburetor.
My engine ran badly after I switched to ethanol gas. What now?
Often the ethanol has dissolved old varnish that is now clogging the filter or jets. Replace the fuel filter, refill with fresh fuel, and test again. If it still stalls, the carburetor probably needs cleaning.
Sources
- Oklahoma State University Extension: Ethanol Gasoline Blends and Small Engines
- Kansas State University: MF3068 Ethanol and Small Nonroad Engines
- Briggs & Stratton: Fuel recommendations
- EPA: Final Rule on misfueling mitigation
- EPA: Regulation History of the E15 Misfueling Mitigation Plans
- U.S. Department of Energy: Effects of Intermediate Ethanol Blends
- NC State Extension: Ethanol and Two-Stroke Cycle Engines
- Briggs & Stratton: How to choose fuel
- Briggs & Stratton: Storing your equipment