I guess it depends on the vehicle.. I know with the police cars we had, dedicated CNG and Bi-Fuel, they wouldnt run with the gasoline cars. The power curve was just weaker. As for the plug wear, I would double check the part number for that vehicle. The ones I used to work on didnt wear the plugs much more than gasoline. Although, you mentioned that the timing has to be set for it, how old is this truck? Is it fuel injected or carburated? That would make a BIG difference, carburated gas burners wouldnt fall out of a tree anyhow, so the difference would be minimal.