Easily done, I know of a piston Islander refuelled with Avtur, but it was spotted before any harm could be done, they were used to handling a Turboprop version, so when a piston one turned up it was missed. Indeed the CAA ordered decals on the likes of the Rockwell Commander 112TC had to have the Wording "Turbo" removied from cowlings or from the likes TurboCharged decals on the fuselages in case Turbo was mistaken for Turboprop.