Can You Run Ethanol Gas in Your Jet Ski?

What kind of gas should someone run in their jet ski has become a super common question these days. With the rise of ethanol in our gas along with more blends, the question needs to be answered.

Can You Run Ethanol In A Jet Ski?

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 jet ski engine. Though, I suggest 2-stroke jet skis avoid ethanol gas.

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.

What Is Ethanol Gas?

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 ethanol is an octane booster, which cuts down on knocking.

The problem with ethanol is that it’s less energy dense than pure gasoline, and it loves water. That water loving part is a problem for jet skis and boats.

What Jet Skis Are Fine To Run Ethanol Gas?

The adding of ethanol to gas 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 for your jet ski.

Every jet ski 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 jet skis I would worry about are 2-strokes, especially since the ethanol loves to damage the engine.

If you have a 2-stroke jet ski, it’s best you avoid gas with ethanol in it.

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

Is Ethanol Gas Bad For Your Jet Ski Engine?

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

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

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

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

Is E10 Better For Jet Skis?

E10 gas, 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 jet skis, especially the knocking.

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

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

Where Ethanol Becomes A Problem For Jet Skis

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

When ethanol is exposed to enough water, it causes separation, leaving you with a nasty mixture of water and gas (makes bad gas). This water can come from the humidity in the air (condensation) or the simple fact that jet skis operate in a wet environment, so water is everywhere. Water always finds a way and easily makes friends with ethanol in the gasoline.

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.

For winter storage, I lean more towards keeping the gas 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 gas than a whole tank of bad gas. Also, some storage places require you store your boat near empty for safety concerns. I agree with the storage places as my jet ski 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 gas, as they hold quite a bit of 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 jet ski 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.

What Gas Is Best For A Jet Ski?

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

You will also need to stay under 10% ethanol too, even with premium gas.

The type of gas the manufacturer of your jet ski recommends will be located on a sticker near the gas cap. I know some manufacturer will say you can run regular, but you will get better performance out of your jet ski if you run premium, especially if it’s supercharged.

Is Ethanol Gas Better For The Environment?

The push for ethanol gasoline was because it oxygenated the gas 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?

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 gas and how we may have been wrong.

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