Just as a follow-up to this, a bit of additional explanation that might be useful in explaining the risks associated with using E10 Bio-ethanol fuels.
E10 fuel includes a 10% (hence E10, as opposed to the higher-percentage alternatives, such as E15 through to E85 that also exist) blend of Ethanol Alcohol. This is a so-called "bio-fuel", manufactured from plant extracts etc, and is supposed to be the "green fuel" of the future.
As we already know, however, the appeal of growing crops for the production of bio-fuels is a mixed blessing. Yes, it offers an alternative source of oil, and releases the stranglehold that the OPEC nations have on the rest of the world, but it simultaneously encourages farmers to move away from food-based crop production into wholesale planting of inedible crops for bio-fuel manufacture. We have already seen the effect of this on countries where vast tracts of forest have been decimated in order for the land to be set aside for the growing of bio-fuel crops. Food shortages could (and some say, already are) occurring as a result.
So we have a fuel that is supposed to be "green"? No, we don't.
Biofuels such as E10 have a couple of significant disadvantages. On the one hand, they are less efficient, and vehicles using them will typically consume 3% more fuel than those using conventional fuels. That's also 3% more of the 90% conventional fuel content that the 10% ethanol is originally mixed with, which just about brings you back up to where you started. Hardly worth the effort, especially as E10 fuels are usually more expensive than normal fuels.
Secondly, the volume and nature of polluting gasses and chemical compounds released into the atmosphere by engines running E10 formulations is actually higher and more noxious than that emitted by the same engine using conventional fuel. This fact is further exacerbated by the fact that the ethanol content of the fuel also has a deleterious effect on the effectiveness (over time) of the engine's own monitoring system (if it is fitted with devices such as in-line oxygen sensors) and also elements within a catalytic converter, if part of the exhaust system.
However, these issues are not the concerns to which Glenman's original post refers. Because Ethanol is an Alcohol, it has different properties to conventional fuel mixtures, and some of these are not beneficial to the internal working of the engine. Firstly, ethanol has the ability to attract and absorb water. If your vehicle (or, most especially, boat, lawnmower, or other petrol driven device) is stored for any length of time in a damp environment, moisture will be absorbed into the fuel. This not only leads to a dilution of the fuel and a reduction in its effectiveness, but it can also lead to phase separation, water contamination and ultimately, the rusting of internal components.
In vehicles used regularly, this will be of minor concern, but for boat owners and gardeners, this is an important factor. The bottom line is, E10 fuels should never, ever, be used in boats, and only as a last resort in smaller petrol-driven devices, such as strimmers, chainsaws and the like. In the case of the latter, E10 fuels will also result in uneven running and the possibility of repeated stalling.
Furthermore, ethanol is regularly used as a solvent and cleansing product. It's great stuff. It dissolves lots of messy residues and can be used to remove ingrained dirt, grease and grime from all sorts of surfaces. Sorry, did I say grease? Yes, ethanol is a great de-greasing agent, so what are we doing putting it anywhere near cars? Useful on the outside of the engine perhaps, provided you rinse it off afterwards, but inside?
Ethanol also causes leeching in many plastics and rubbers, resulting in these materials drying out and becoming brittle. Many cars, particularly older cars, use o-rings, seals and hoses made from just these kinds of materials, and E10 fuels will, in a remarkably short time, lead to these components becoming unstable and prone to fracture and cracking. Hoses need to be flexible to absorb the vibrations of the engine, and they bridge gaps between rigid aluminium or kunifer-based fuel pipes that link the tank to the delivery system. If they become hardened and brittle, they will eventually break, and this can lead to fuel leaks and, potentially, a serious fire hazard.
Not only that (and this list goes on!), but as a cleansing agent with corrosive properties, E10 fuels will also lead to the release of small particles of rust, dirt and sediment from within older-style steel fuel tanks (where rusting will be accelerated by Ethanol's water-retaining tendencies) potentially leading to the clogging up of fuel filters and eventual fuel starvation at injectors and carburettors.
So, all in all, E10 fuels are a very mixed blessing. There is plenty of information on the Internet now that goes into this problem in great detail, including this useful (if somewhat scientific) article:http://www.ewg.org/reports/Ethanol-Gasoline-Fuel-Blends-Human-Health-Risks-and-Engine-Performance-Issues
If in doubt, don't use the stuff. Most manufacturer's websites now include a list of their vehicles that can use E10 fuels, and those that can't, so check through Google. Generally speaking, however, cars built in the last five years or so should be OK, but also be aware that if your car uses a turbo, you may have additional long-term issues to consider!