The thing which concerns me about MoGas is not the actual fuel itself. I drive around 14,000 miles/year in a 24 year old car (with an engine block which was designed in the 1950s). It was perfectly happy when I converted it to unleaded fuel, and has been happy ever since. I know it's not a direct comparison because the construction/material of aircraft engines is very different to car engines, but with the correct tuning and other minor mods, our engines could run on just about any petrol you care to put in them.
The thing which concerns me about MoGas is quality control. I'm pretty sure we've all experienced a bad tank of fuel in our cars. You pull into the petrol station, everything is fine. You fill up, and 20 miles later you notice a little blip in the power which wasn't there before. Not enough to worry about, but you notice it. It gets worse over the next few miles, but then it settles down and you get used to it. You maybe think "I'll take it to the mechanic if it carries on." But that's not necessary, because it doesn't get any worse. Then, you fill up again, and within 20 miles of this fill-up everything is back to normal. "Hmm, must have just been a bad tank" you think to yourself, and that's the end of it. There's a theory that this is most common after the petrol station receives a delivery, because pumping all that fuel into their storage tanks stirs up the crap at the bottom of their tank. I'm not 100% convinced, but it's certainly possible.
Well, that's ok for cars. But not for aircraft. At least, not for aircraft that I'm flying in, nor my family and friends. Just as with the car scenario, you'd probably get by without it causing too much trouble. Certainly in the cruise it wouldn't matter too much. But then you go to put the power in for a go-around when some idiot lines up as you're at 50' on short finals and the engine splutters, just for a few seconds. Even in this situation you may get away with it, but I guarantee your heart would be beating a little faster once you've got a positive rate of climb.
Whatever we get, it must have the same level of quality control as what we currently have. If they can guarantee quality, I'll be happy.
FFF
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