E10 Fuel

We bear no responsibility for the information on this page as it is all snippets that we have found on the net. You must make up your own minds as to it’s validity.

Can you use E10 for 2 stroke?

E10 fuel can also cause problems with two-stroke engines that run on a petrol-oil ‘pre-mix’, as the ethanol doesn’t allow the oil to mix properly with the fuel. This can lead to greater engine wear and tear.

Although the Government has said that E10 petrol is compatible with 95% of petrol-powered road vehicles, it has acknowledged that some older boats with petrol engines may not be compatible with the new fuel. The Government has advised that boat owners and operators should check their vessel’s manual or ask the manufacturer or dealer before filling up with E10.

If your boat is not compatible with E10 fuel, then you should continue to use E5 ‘Super Petrol,’ which will remain available at many kerbside filling stations after E10 is introduced. Prolonged use of E10 petrol in a non-compatible engine is not recommended and may cause harm to the vessel.

However, if your boat’s engine is compatible with E10 petrol, then there is no reason why you cannot mix the two grades of petrol when filling up.


Ethanol, ethyl alcohol, is made from corn, sugar cane and other grains. Alcohol is an excellent cleaner, solvent, anti-freeze and most importantly, ethanol is hygroscopic, meaning it will absorb large amounts of water. Boaters often store fuel longer than that recommended for E10 (90 days). Cars, unlike boats, usually replace fuel every week or two, and will successfully prevent water-contamination/phase separation, which is when the weight of the ethanol and water sink to the bottom of the fuel tank and get picked up by the motor’s fuel system. (Even small amounts of water can harm the fuel system). Boat engines live in a water environment; alcohol petrol loves to absorb water. E10 fuel can absorb large amounts of water into the fuel tank.

Mercury outboard and sterndrive products should NOT have fuel added that exceeds 10% Ethanol
The use of alcohol in gasoline is increasing as an alternative to petroleum based fuel and used in reformulated (oxygenated) fuels, however, some drawbacks you may encounter to this technology for use with marine engines are:

Corrosion of metal parts
Deterioration of rubber or plastic parts
Fuel permeation through rubber fuel lines
Starting and operating difficulties
What is Ethanol?
Ethanol is an alcohol made from sugar cane, wheat and many other organic materials
Ethanol is often blended with gas (E10) and has been used in the automotive industry since the early 1980s
More recently, Ethanol has been made available as E85 (85% ethanol) for flex fuel autos only
Why E10 Blends?
Ethanol can be used to meet EPA requirements for a cleaner burning fuel
Ethanol slightly improves Octane Rating
Ethanol can help reduce our dependence on foreign oil
The EPA does not permit more than 10% Ethanol to be added in fuels labeled as gasoline
E10 Blend – Properties
E10 absorbs water readily and easily
If sufficient water is absorbed, “phase separation” can occur-water and ethanol will settle to the botton of the tank and gasoline will be on top Ethanol Phase Seperation
Phase separation cannot be reversed with agitation or fuel additives
Boundary layer can contain corrosive componds which can cause corrosion in aluminium fuel tanks
E10 Blends – Compatibilty
Fuel system components of Mercury Outboard and Sterndrive Engines can and will withstand up to 10% Ethanol content in gasoline

Water contamination of fuel is the big issue and concern

The best advice we have for customers is to empty the fuel tanks for long term storage. Alternatively, keeping the fuel tank full reduces the amount of exchange between the fuel and air that might bring in condensation

Phase separation essentially means that the ethanol in the fuel has attracted water (usually already present from condensation and/or other sources) into the fuel mix. When the right amount of water enters the mixture, most of the ethanol and water will tend to separate from the fuel (into a different “phase”) and drop to a lower level or layer inside the tank (water is heavier than fuel). If this layer of concentrated ethanol and water is drawn into the engine’s fuel system, significant damage can occur. Further, the level at which phase separation occurs is determined by a number of variables, one of which is the temperature of the environment. This may help to explain why some regions of the country may be more affected by ethanol than others. Mercury Marine believes this higher ethanol exposure has caused product failures in fuel system components on two-stroke and four-stroke product.

Ethanol has very different solvency behaviors than gasoline and is a proven contributor to the deterioration of certain rubber and/or plastic components and electrical potting compounds. Mercury is aware of this potential and is constantly working to implement material improvements to better withstand the effects of ethanol. One such improvement in place on all 75-115 hp four-strokes since 2006 and Verados since June 2007 (most easily identified by the polished chrome graphics package) is an improved float switch in the fuel supply module that ensures the integrity of the switch itself, even when exposed to higher ethanol concentrations. This change alone should address the majority of ethanol-induced product failures within the fuel system.

Mercury continues to monitor the ethanol situation worldwide and makes every effort to upgrade materials as necessary to ensure the continued reliable, durable operation of all of its outboard products.