Fuel cost for a Cessna 172 is maybe 50 $/hr (10 gallons per hour times 5$ per gallon), while the plane rental (wet, including fuel) is about 180 $/hr. So, even

Fuel cost for a Cessna 172 is maybe 50 $/hr (10 gallons per hour times 5$ per gallon), while the plane rental (wet, including fuel) is about 180 $/hr. So, even if you’d get the fuel price to zero, you’d reduce the rental price by at most a third.