Guys E10 is ethol alchole, which is hydroscopic, which means it will absorb moisture. here in lies the problem, when to moisture combines with the ethanol it becomes corrosive, it will eat out the fuel system, unless the tank lines and injectors are synthetic or dont contain aluminium or glavinised steal. e10 also has less energy the normal fuels, so you use a little more than normal 91ulp, but because it burns SLOWER it raises the RON of the fuel ie, 91 ulp + 10% ethanole = @ 93.5 RON and this will (if you engine is able to via ecu adaptive learning) give you more torque and therefore technicaly more performance. so if it is cheaper gives you more bang and the car is designed to use it, go ahead, BUT i will never put it in my car. as it should in effect cost 3 to 4 cents per litre less than 91ulp due to the increases fuel consumption. do some research to who makes ethanol and political donations to parties, and who is in power and the legislation of that state in regard to renewable fuels, YOU may be suprised.