Remember also that air cooled engines can sometimes burn a little more oil than liquid cooled ones, and for that reason they usually come equipped with low oil shutdown systems when they are to be used in an extended run type of situation, such as on a generator. Trash pumps may or may not have this option from the factory, depending on the engine manufacturer.
If they don't, and you increase the run time by adding an external fuel tank, be aware that you need to remain vigilant about checking your oil...
