Fuel economy depends on several factors: Hydro system Mower weight Terrain Deck design For instance, my 28hp EFI Kohler effortlessly powered many mowers in the past. It wasn't until mowers got over 1200lbs and used hydro pumps 2x's larger than most that this engine suddenly became overwhelmed. Todays engines are working harder with these bigger more complex hydro systems, bigger spindles, pulleys, blades, and now some mowers that are 1500+ lbs! My old Dixie Chopper was 900 some pounds. Older Lazers were right at 1000 pounds.