It just depend's.Daily driver,light car or truck, the 240 hand's down.Heavy towing or work truck the 300. I once replaced a 250 in a 66 chevy with a fresh built 292.It was stronger,slower,and used more gas.Thought I needed the extra power,but the truck with the 250 was nimble and quick,and about a 100 more miles per tank.Wintertime driveing in Alaska with the 292,I straped two jerry cans of gas in the bed just to be safe.