Let’s Discuss Running Ethanol Gas In Your Jet Ski

Is it safe to run ethanol fuel in your jet ski? Yes, I find that it’s okay to run ethanol gas in your jet ski, so long as it’s 10% or less. This type of gas often goes by E10 and will be fine to run in your engine.

Though, I suggest 2-strokes avoid ethanol fuels.

Do NOT use E15 or 15% ethanol gas in your jet ski or boat!!! Only E10 (10% ethanol) or less is okay.

E15 may become more common and may even become the “regular” 87 gas that everyone picks, so please pay attention while at car gas stations.

There is more to uncover, so let’s talk about it below.

Ethanol Fuel Explained

Ethanol is produced from removing the starch or sugar portion of corn and fermenting it.

You can see the process here.

Ethanol is used as an “oxygenate” for gasoline to cut down on air pollution from hydrocarbon emissions. Not only that, but it is an octane booster, which cuts down on knocking.

The problem

The problem with it is that it’s less energy dense than pure gasoline, and it loves water!

That water loving part is a problem for boats.

2-strokes, Avoid It

The adding of ethanol to fuel started around the mid-2000’s, with most of the fuel in America having at least 5% by 2013 with the push to 10% after that. As of 2022, there seems to be another push to 15%, so please pay attention at the pumps as most did not realize the jump to 10%. You should avoid 15% ethanol.

Every manufacturer has known about these fuels for a good bit, and the E10 that is used doesn’t seem to affect 4-stroke engines.

The only waverunners I would worry about are 2-strokes, especially since the ethanol loves to damage the engine.

If you have a 2-stroke, it’s best you avoid ethanol!

If you have a 4-stroke, you can run 10% or less ethanol gasoline.

How It Affects Your Engine

Unless you have a 2-stroke, your engine will be fine with E10 or less, as it was made when the standards started coming into place.

Ethanol fuel also hurts 2-stroke engines lubrication because of its nature to attract water. 2-stroke engines combine the fuel and oil to operate, but when there is too much water in the fuel, it keeps the oil from contacting the metal parts and wears 2-strokes out more. 2-strokes operate in a very wet environment, so ethanol fuel and 2-strokes are not a good combination.

4-strokes don’t combine the fuel and oil.

As for 4-strokes, 10% or less is not a problem for your engine, as this video explains.

E10 For Jet Skis

E10, 10% ethanol to 90% gasoline, is a double edge sword.

E10 burns cleaner, helps fight against knocking as it’s an octane booster, and it’s cheaper. All these pros are a good thing when it comes to watercraft, especially the knocking.

Water Loving

But the biggest crux for ethanol gasoline when it comes to watercraft engines is that it is water loving and, over time, can cause phase separation of the fuel if enough water gets in the fuel.

Another problem with ethanol gasoline is that it is less energy dense than ethanol-free fuel. You don’t go as far, and you don’t get as good MPG!

Where Ethanol Becomes A Problem

There is one huge problem with ethanol when it comes to engines, and it’s that it loves water.

When ethanol comes into contact with a significant amount of water, it leads to separation, resulting in an undesirable mixture of water and fuel, often referred to as “bad gas.” This water intrusion can occur due to the humidity in the air, which leads to condensation, or simply because Personal Watercraft (PWCs) are used in wet environments where water is omnipresent. Water inevitably finds a way and readily bonds with ethanol present in the gasoline.

Storing fuel

If you’re storing your jet ski for the winter, I suggest storing it full of gas or with very little gas in the tank.

Add Fuel Stabilizer

For winter storage, I lean more towards keeping the tank almost empty (one or two bars) and putting stabilizer in it. You can’t stop the water, so I rather have a little bit of bad fuel than a whole tank of bad fuel.

Also, some storage places require you store your boat near empty for safety concerns. I agree with the storage places as my PWC is near my home and I rather have it near empty. Along with gas-caps on jet skis and boats being easy to open, I don’t want them being a target for people who steal, as they hold quite a bit of gas.

Fresh Gas

There is also no additive that brings bad gas back, only adding fresh gas will work. So when the season starts, I add fresh 93 octane gas to my Sea-Doo Spark to bring some life back to the gas.

Important: Do not swap between ethanol-free gas and ethanol gas; pick one and stay with it. You’re more likely to have phase separation switching between the two, especially coming out of storage, and end up with bad gas.

Premium Fuel Is Best

The best gas for a watercraft is premium (91/93 octane) but all non-supercharged models will run regular (87 octane) just fine. You will get the best performance out of your machine if you run premium, but it’s no big deal to run regular in a non-supercharged models.

You will also need to stay under 10% ethanol too, even with premium fuel!

What the manufacturer Says

The type of fuel the manufacturer recommends will be located on a sticker near the gas-cap.

I know some manufacturers will say you can run regular, but you will get better performance out of your craft if you run premium, especially if it’s supercharged.

Is Ethanol Fuel Better For The Environment?

The push for ethanol gasoline was because it oxygenated the fuel and cut down air pollution from hydrocarbon emissions.

It also was to cut back on fossil fuels, so it would seem to be a win-win type of thing?

Maybe Not

Now that time has passed and new studies done, the answer is not so clear anymore.

This video does a great job showing the studies, the thought process of using ethanol fuel and how we may have been wrong.



I started working at a power sports dealership in 2007, I worked in parts, service counter, and as a technician before moving to sales in 2013. I created in 2014 to answer common watercraft questions I would get from people. Now managing the site full-time, I continue to provide advice and web tools for my readers about watercraft. I've owned several watercraft, with a Sea-Doo Spark as my current main PWC.

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