Thread: E10?

It eats rubber.

High concentrations of ethanol are also corrosive. But that's way above E10. At E10 levels "most" fuel systems are completely fine, but not all. Really depends on the grades and formulations used for seals, diaphragms, etc. Some manufacturers haven't specifically tested, so err on the side of caution. Others have tested and seen issues. Additionally ethanol-blend fuels shouldn't be used in/as 2-stroke (just like premium in that regard) as it degrades the function of the lubricant.

The major issue with ethanol in petrol is not that it eats rubber. The major issue is that it is hygroscopic, that is, it attracts water, and is miscible with water in all ratios.

Petrol is not miscible with water, and water in your petrol tank stays as a discrete layer in the bottom (since it is denser), and is prevented from entering the rest of the fuel system by the gauze filter on the suction pipe out of the tank, which will not pass water drops while it is wet with petrol.

But ethanol, since it mixes freely with petrol, as well as with water, provides a mechanism to distribute water throughout the fuel system. When the engine is not run for a while, the petrol evaporates, leaving the water, which then corrodes the zinc or aluminium allay parts of the fuel system, with the oxide flakes produced blocking narrow passages.

This is a particular issue with outboards, since they operate in a humid environment, ensuring that the any ethanol in the fuel has plenty of water vapour to absorb, and in addition they are typically unused for long periods.

Any small motors that are not in continuous use will have the same issues, but it becomes less of a problem in very dry climates.

If you use mouthwash, it probably contains ethanol, which is why I don't drink it.

so, unlike cars, an outboard fuel system is open to the atmosphere?

I really dont understand how/why engine manufacturers get away with using bad rubber,, car engines have been fine with ethanol for decades

As JD said my understanding is it's all to do with it being hygroscopic.

Actually am old friend who's business was OPE had a container of e10 mix and left it for a few months to show customers why they shouldn't use it, it wasn't pretty.

Originally Posted by Pedro_The_Swift

so, unlike cars, an outboard fuel system is open to the atmosphere?

I really dont understand how/why engine manufacturers get away with using bad rubber,, car engines have been fine with ethanol for decades

All fuel systems vent to the atmosphere, boats operate in a higher humidity.

all modern fuel systems are closed.
have been for a long time.
so e10 can only absorb whatever air is in the tank, none from outside.

yes they sometimes VENT to the atmosphere(one-way pressure release),,,
usually on very hot days
like LPG tanks,, except not so explosively