Simple And Advanced Ways To Calculate Fuel Mileage

Even though that at the time of this writing fuel is relatively inexpensive, it’s good to get into the habit of knowing how to calculate fuel mileage to maximize fuel efficiency.

There are three ways of calculating mileage.

1. Dividing miles traveled by gallons used.
2. Using Garmin’s ecoRoute.
3. Using a ScanGauge II.

Dividing miles traveled by gallons used

Step 1. Fill up the tank; reset trip odometer to 0.

Self explanatory. If you don’t have a trip odometer, write down the mileage on your odometer at the time of fill-up.

If you need to write down the mileage, I strongly suggest writing it on a small memo pad that you can put in the glove box for easy retrieval later.

Step 2. Drive as you normally would.

Self explanatory.

Step 3. At next fill up, divide miles traveled by gallons it took to fill the tank.

Example:

The trip odometer reads 275.4 miles traveled since last fill-up. Write this down.

If you don’t have a trip odometer, subtract mileage before fill-up to the mileage you have now. If you had 82191.6 miles on last fill-up and have 82467.0 now, subtract the then-mileage from the now-mileage to get your result, which for this example would be 275.4.

On fill-up, we’ll say a total of 13.12 gallons was needed to fill the tank. You get this figure directly from the display on the pump itself (or on the receipt).

Divide the miles used by the gallons needed to fill up, which in this case would be 275.4 ÷ 13.12.

Tip: Use your cell phone’s built-in calculator function to make this easier. Even the cheapest of cell phones have a calculator in it.

The result is 20.99 miles per gallon.

This figure is an overall mileage result. It is a combination of both city and highway driving.

Using Garmin’s ecoRoute

This was a new feature introduced into Garmin nüvi GPS devices in 2008. It is available even on the cheapest model, the nüvi 205, which at present retails for $109.99 with free shipping at NewEgg.

ecoRoute, like all other features of the nüvi 205, is completely free. All it takes is to update your nüvi via Garmin’s updater program. This can be accessed by registering your nüvi at http://my.garmin.com, then clicking on the myDashboard link to update.

All it takes to use ecoRoute is to configure a vehicle profile first, like this:

If you don’t know what your vehicle’s fuel economy rating is, go to www.fueleconomy.gov, specifically this address, select your year/make/model and you’ll get the information you need.

After that you establish a "Driving Challenge", set the current price of fuel per gallon, then read reports afterwards for destinations you go to, like this:

ecoRoute is mostly accurate. It’s obviously not perfect and does not take into consideration things like wind drag, weight of vehicle and other things. However generally speaking it’s fairly close to what you’re actually achieving for gas mileage.

Using a ScanGauge II

ScanGauge is for those who want exact mileage reports. This is the most expensive of the bunch at around $170, however the advantage is that it DIRECTLY connects to your engine’s computer to get its information via an OBDII (On-Board-Diagnostics) connector. This connector is already in your car.

If your car is a 1996 or newer, you can most likely use a ScanGauge. The compatibility list for cars is here.

ScanGauge II gives you real-time mileage reports directly from your engine’s computer. In addition to mileage, it will also report fuel rate, battery voltage, coolant temperature, intake air temperature, RPM, vehicle speed, engine load, throttle position, ignition timing and more. It can even read "trouble codes" as well.

The display also doesn’t have to be amber. You can change it at any time to one of 63 different colors. And yes it has a backlight for night use with adjustable brightness.

Possibly the best part about the ScanGauge is that this is a no-tool installation. No drilling or custom mounts required.

Having this many gauges is usually only reserved for luxury vehicles, but with the ScanGauge you get everything for a whole lot cheap than a luxury car.