E10 works in many engines, but read the manual first
Mercury states that its current petrol engines can handle at most 10 percent ethanol, meaning E10. Suzuki's manual for the DF15A/DF20A sets the same limit. That tells you nothing about older marine engines, hoses or tanks. Look up the manual for your specific engine and check the whole fuel system before switching fuel.
Alkylate petrol works fine if the product meets the engine's fuel requirements. The oil then has to be handled correctly for the engine type: four-stroke, premix or separate two-stroke lubrication.
Three things to check
| Property | Why it matters |
|---|---|
| Ethanol content | Must be within the limit of the engine and fuel system. |
| Octane rating | Must at least meet the manual's requirement, measured with the right system. |
| Oil mixing | Must suit the engine's lubrication system and the specified oil grade. |
Suzuki's manual requires at least 91 RON and no more than 10 percent ethanol. Other engines may have different requirements. American manuals often state octane in a different measure from the one shown on Swedish pumps, so read the full specification.
Alkylate petrol is not always ready-mixed for boat engines
Alkylate petrol comes in two versions. Pure alkylate petrol is for four-stroke engines. Premixed alkylate with 2 percent oil is made for air-cooled two-stroke engines such as chainsaws and trimmers. A water-cooled outboard should not run on that mix just because it is also a two-stroke, since a marine engine has its own oil and mixing requirements.
If the engine has a separate oil tank, lubrication is handled from there, so don't add your own oil to the petrol. If you are unsure which product is right, ask an authorised dealer workshop.
Ethanol, water and winter storage
Mercury explains that petrol containing ethanol absorbs water. With phase separation, water and ethanol end up at the bottom of the tank and the petrol above is degraded. An additive won't make contaminated fuel good again. If the engine runs poorly or you find water in the filter, have someone look at the tank and fuel system.
How you should store fuel over winter depends on the tank system among other things, and the manual describes what applies to your model. Read more about winter storage. Fresh petrol and a clean filter do more good than a bottle of additive.
How to choose fuel
- Look up the model, serial number and the right manual in the engine catalogue.
- Write down the ethanol limit, octane requirement and oil requirement.
- On an older installation, go through the tank, hoses, fittings and filters one by one.
- Read the product sheet for the fuel. The colour of the can tells you nothing.
- Note what you fill up with and keep an eye on whether the engine runs differently or leaks.
You can work out what a trip costs with the fuel tool. More expensive fuel doesn't lower consumption on its own. A faulty or badly adjusted fuel system won't improve with different petrol either.
Frequently asked questions
Can all outboards run on E10?
No. The manufacturers' statements apply to the engines they list. On an older engine, the tank and hoses need to be checked separately.
Can I use chainsaw alkylate petrol in my boat engine?
Read the specification first. Premixed fuel for air-cooled two-strokes may have the wrong oil or the wrong ratio for an outboard.
Can a fuel stabilizer make bad petrol good again?
No. Contaminated or phase-separated petrol must be drained and disposed of.
Sources
- Mercury Marine: etanolgräns, vatten och bränsleförvaring mercurymarine.com
- Suzuki DF15A/DF20A: bränslekrav suzuki-marine.gr
- Aspen 4: produktspecifikation aspen.se
- Aspen 2: avsett för luftkylda tvåtaktsmotorer aspen.se