Why?
Don't carry unnecessary items in your luggage compartment. An extra 45 kg (100 lbs) can cost you 2% more in fuel use.

How do I do this?
Don't carry items in your trunk or back compartment that you do not need.

In winter, make sure to not only clear the snow off the top of your car, but clean out the wheel wells too. Snow build up can add significant weight to your vehicle and can affect the handling as well.