Before you even get to the issue of any potential problems with MOGAS, you have the practical problem of getting it into your tanks. I could theoretically use it in my aircraft, but I don't fancy driving to the airfield with 120 litres of petrol in tins in the back of the car.
Once you're away from your home airfield you have the further problem of where to find anything but AVGAS. I've never seen an airfield with a MOGAS pump. Taking cans with you and getting a taxi to a petrol station seems a lot of messing around, and the taxi fare would probably wipe out any cost saving on the fuel itself.