With all the talk regarding high gas prices and its effect on peoples’ wallets, we’re all particularly interested in a car’s gas mileage. Everyone wants to save a few bucks, but is there more to gas mileage than just a car’s miles per gallon?

With all the talk regarding high gas prices and its effect on peoples’ wallets, we’re all particularly interested in a car’s gas mileage. Everyone wants to save a few bucks, but is there more to gas mileage than just a car’s miles per gallon?

First off, the United States government has done a pretty good job keeping track of fuel economy for most every car on the market. Fueleconomy.gov has a searchable database to find your car’s fuel economy information, as well as other valuable stuff. Very good resource, especially when you get to big SUVs like the Hummer and the Porsche Cayenne

Gas Mileage as a Diagnostic Indicator

While it’s all well and good that higher gas mileage can save you money at the pump, keeping track of your car’s gas mileage when you fill up can be useful in figuring out if your car is having any serious problems.

In my old 1993 F-150 (XL, Flareside, 4.9L I-6) I noticed that my fuel economy had dropped from 14mpg to 8mpg over the course of a few weeks. At first I attributed it to driving to closer destinations or mashing down on the gas pedal too much, but when it got below 10mpg it sent up a red flag. After some basic diagnosis, I determined the culprit was a rusty distributor cap and rotor. Corrosion is a bad thing.

The fix was about 15 dollars (USD, approximately 3 and a half euros) if I remember correctly, and was detected because I was paying attention to the truck’s gas consumption. All it takes is a trip odometer and a calculator.

Of course, there is more at play than just a distributor cap. If your gas mileage is down by one to two miles per gallon, you should check your tire inflation. Generally most people overlook the importance of proper tire inflation, but this can increase fuel economy and result in better handling and driving character.

And of course, as is my problem right now, if your mileage goes from 21 mpg to 13mpg, you just might have a hole in your gas tank. The obvious test is to look under your car for a giant puddle. Try not to cry when you do this. Yes, you did just throw away 10 dollars at the gas pump. Of course, if you’re lucky the hole is high on the gas tank and you won’t leak fuel if you don’t fill the gas tank past that level. Right now I can only fill my car to 3/4 of a tank, because I’m not paying for a new gas tank.

Not all causes of lessened fuel economy are as simple as these problems though. If your tires are in good shape and all the simple things are fixed, it might be time to take the car to a garage. There could be a fuel pump problem or further difficulty with electronic fuel injection.

It’s important to be sure that when you’re comparing values they were obtained under similar circumstances. If you notice a drop from 28 mpg to 21 mpg and think that something is wrong, but you drove the 28 mpg on the highway and 21 in the city, that’s perfectly normal.

Measuring your fuel economy, just like keeping your tires properly inflated, is a quick and easy way to make sure that your car is functioning properly, and is also something you can tell to your garage as an indicator of a problem. So get out that calculator already.