Depends...The Spitfire(30 mpg having fun or 38 mpg highway) has an 8 gal tank and likes (89 octane) about $3.50/gal here. Work van (16.5-17 mpg) 27 gal reg $3.32/gal. Cessna (20 mpg in cruise) 37 gal useable 100 low lead about $6.00/gal.