The US. Environmental Protection Agency (EPA) is responsible for providing fuel economy (gas mileage) information that is posted on the window stickers of new vehicles. The information provided is an estimate that helps consumers comparison shop. The reason the EPA provides estimates, rather than concrete numbers, is that everyone’s gas mileage will vary depending on a number of factors: weather, road conditions, driving and maintenance habits and use of air conditioning.
So how exactly does the EPA determine gas mileage information? The EPA’s gas mileage ratings are based on a series of tests that they conduct under controlled conditions.
Gas mileage ratings fall into two categories, and each vehicle is tested for both categories. The first category is city driving. When this category is tested, the vehicle is not used for an entire night (so it starts “cold”), and then it is driven during rush hour traffic when the vehicle must stop and start often.
The second category is highway driving. The EPA begins this test with a “warm” vehicle, which is driven across a variety of roads including highways, interstates, freeways and country roads.
All makes and models of vehicles are tested in the same way. However, the variables that can affect a vehicle’s mileage include:
- The make and model of the vehicle.
- Engine condition. An engine that is in good condition will run more efficiently and the result will likely be better gas mileage.
- Road conditions. Vehicles get better gas mileage when they are driven on smooth roads than when they are driven on roads full of bumps and potholes.
- Lots of stopping and starting or being stuck in traffic.
- Extreme weather changes.
- Individual driving habits. Factors such as speeding, using cruise control and frequent braking can impact gas mileage.
- The amount of gas in the tank. When a gas pump automatically stops when the tank is ‘full,’ it very often is not really a full tank.
So when you’re shopping for a new vehicle, be sure to check out the information provided by the EPA on the window sticker. In addition, you should keep in mind that if fuel savings is your goal, you should bypass four wheel drive vehicles if possible. Four wheel drive vehicles use a lot more gas, even when you’re not actively using the 4WD feature. And even if the upfront price is a little more, a car that goes a lot of miles on each gallon of gas will cost you less to operate over the long run – not to mention making less of a negative impact on our environment!
