There are a few things you can do to ensure you are getting better gas mileage when towing your trailer. One of most important things you can do to ensure you are getting the best mileage is to make sure your trailer has proper tire pressure. Over inflated and under inflated tires can have a major impact on gas mileage. Another key to ensuring you are getting the most out of every tank of gas when towing a trailer is bringing your trailer in for regular maintenance. Ensuring the bearings are packed properly, the running gear is in good shape and other maintenance can have a major impact on your gas mileage.