In the 1980's when diesel was actually cheaper than gasoline my dad had a friend that ran diesel in a gas engine. He would start his Silverado on propane, get the engine good and hot, hit the switch and switch it so that diesel was going through the carburetor into the engine. It ran just fine. When he was getting close to where he was going he would switch back to propane and let the engine clean out for a while before shutting it down. Not gonna work on a modern vehicle.....