The reason your dad gets better mileage is because of the use of his right foot. The younger the driver, the heavier the foot. If you start driving like your dad your mileage will go up considerably. The modification that gets the best mileage is the driver.

 

Aye, my Civic averaged 35-38 during delivery driving, which meant right foot planted during acceleration. After the accident, it got 30. Things I found out:

1: Easy on the throttle. It may be a 1.6, but it takes lots of gas to go fast.

2: Keep nothing in the car except the toolkit and the spare.

3: Running 25 PSI tire pressure? Good for drag, bad for fuel economy. Up the PSI to the max for the tires on the wheels for best fuel economy and wet traction.

4: A/C on all the time? I almost never used it. Tiny engine has to push an A/C will eat your fuel economy. At high speeds (65+), though, it's better than windows down.

5: Check your alignment. If your tires wear wierd (and I don't mean fronts wear fast and the rears don't that's normal), if it pulls, if the steering wheel is crooked, if the car is not absolutely straight, maybe get an alignment. It also makes less vibration (second to BALANCING your tires) and lowers tire wear.