the numbers are not going to tell you what your gas mileage will be; it is just an indication of the relative fuel economy of the vehicle.

Okay, so what do those numbers on the window sticker mean and how do they arrive at them?

EPA fuel economy estimates are posted on the fuel economy label of all new vehicles.

The only intended use of these values is for comparison among the different vehicles. Fuel economy estimates are generated from data taken during a laboratory test using pre-production prototype vehicles under extremely controlled conditions using a professional driver, with the vehicle operating on an instrument similar to a treadmill. The comparison of current vehicle fuel economy to the EPA fuel economy estimates is to let you compare apples to apples.

The EPA GAS MILEAGE GUIDE, available at each dealership, points out that the actual mileage when driving a vehicle may differ considerably from the estimated mileage. The guide also describes how vehicles are tested under identical conditions to ensure that the results can be compared with confidence.

The EPA GAS MILEAGE GUIDE also points out that the city fuel economy estimate simulates a 7.5 mile stop-and-go trip with an average speed of 20 mph. The trip takes 23 minutes and has 18 stops. About 18 percent of the time is spent idling, as in waiting at traffic lights or in rush hour traffic. Two kinds of engine starts are used: the cold start, which is similar to starting a car in the morning after it has been parked all night, and the hot start, similar to restarting a vehicle after it has been warmed up, driven and stopped for a short time.

The test to determine the highway fuel economy estimate represents a mixture of "non-city" driving. Segments corresponding to different kinds of rural roads and interstate highways are included. The test simulates a 10-mile trip and averages 48 mph. The test is run from a hot start and has little idling time and no stops.

The EPA GAS MILEAGE GUIDE explains that the actual test results are adjusted downward to arrive at the estimates used in the booklet and on the labels. City estimates are lowered by 10 percent and the highway estimate by 22 percent from the laboratory test results. The guide also points out that traveling at higher speeds lowers fuel economy and traveling at 65 mph instead of 55 mph lowers fuel economy over 15 percent.

Even though these figures are adjusted, they still represent what the average driver will get. Your fuel economy may be significantly higher or lower, depending on how, when, and where your vehicle is driven.

Here are some things you can do to increase fuel economy:

* Combine errands into one trip.
* Turn the engine off rather than letting it idle for more than a minute.
* Have your car serviced as described in the maintenance booklet.
* Keep tires inflated to recommended pressures.
* Anticipate traffic stops.

Here are some things that will lower fuel economy:

* Quick acceleration.
* Traveling at higher speeds. Traveling at 65 mph instead of 55 mph lowers fuel economy by 15 percent.
* Carrying unnecessary weight in the vehicle.
* Revving the engine. This is not necessary for your vehicle.
* Operating your vehicle with the suspension out of alignment or with the wheels and tires out of balance.
* Use of electrical accessories that require high amperage when they are not needed.

Even things beyond your control, such as weather conditions, affect your fuel economy. Driving up steep hills, in rain or snow, and into a strong wind will lower fuel economy. In the lower left corner of the fuel economy window sticker for your vehicle is the range of city and highway fuel economy you can expect to get from your car.

City estimates are lowered by 10 percent and the highway estimate by 22 percent from the laboratory test results.