How many of you know about the hot bulb or hot tube engine? The earliest i/c engines had a chamber leading off the cylinder head, preheated and then kept hot by combustion itself. This sort of engine had the advantage of being able to burn most flammable liquids.
It's most commonly known as an industrial or farm engine but it was used on tractors and the like as well.
In Britain, the mixed petrol and diesel from wrongly fueled cars is bought by canal boat owners with vintage Bolinder and suchlike engines, so you could reasonably find a source of fuel from your local breakdown contractors who have to find a legal and safe way of disposing of the mixture.