Tractors run on diesel...
And I understand the A/F argument, that is what I work on everyday at work. Yeah, running too lean can kill small engines, but that is mostly a 2 stroke problem, and not one that I've ever seen caused by running with ethanol. Around where I come from everyone uses gasoline with ethanol blended in small engines (snowmobiles, 4-wheelers, chainsaws, lawnmowers, weed whips, utility engines, etc) and we've never seen a problem. The stoich A/F of gasoline is 14.7, while the stoich A/F of ethanol is 9. If you're mixing 10% ethanol, that brings the stoich A/F down to about 14.1, which can be a significant amount. Cars deal with this by using O2 sensors to adjust A/F as the EGO gets too low, small engines do not. This is where the assertion that running with E10 can hurt small engines come in, and I'll admit, it is a valid argument, I just don't buy it. First of all, I would expect any small engine without an O2 sensor to be carbureted. On a carbureted engine, the A/F is determined by the jetting, and the A/F is not very consistant when controlled this way, I would expect small engines to be running on the rich side, due to this. It is better to error on the side of rich than lean, which is why you see people trying to get more performance out of small engines by using smaller jets and running lean. Overall, when I look at it, yes, the A/F is leaner when running E10, but I wouldn't expect it to be a problem, due to the way that a normal engine is setup. On the other side of the coin, if I had a performance small engine, in say a racing dirt bike or sled (ignoring the fact that these are already almost always setup to run 100% alcohol), I wouldn't use E10, because these engines are already tuned to run as lean as possible, running ethanol would probably make them run too lean and burn up the engine. On a normal engine, I don't see a problem, and if someone is actually worried about it, put in one size bigger jet, it takes about 5 minutes to do.
