The liquid propane-powered buses of the Proctor School District are really something.
Ask School Superintendent John Engelking.
They're more fuel-efficient and get better gas mileage (.35 per mile compared with .65-$1.25 for diesel), they're cheaper to operate (7 qts. of oil/$5 filter compared to 30 qts. of oil and a $35 filter for diesel) and they've got an unexpected benefit that may have parents running to get their gas-powered vehicles converted.