The average American motorist drives about 10,000 miles per year. The average car gains about 22 miles per gallon of gas. This means that the average car uses just over 450 gallons of gasoline each year.

Following the pair of hurricanes that hit the Gulf Coast in 2005, many areas saw a gas prices rapidly increase by $1.50 per gallon. If prices had stayed at that level, the car owners would have paid about $680 more over the course of a year per car. Prices did not stay at their elevated level for an entire year, however. They settled back to the $2.00 - $2.25 range across most of the country.

If you are an average American driver, every time the price of gasoline increases by 25 cents, your monthly gas bill increases by $10. Similarly, using regular unleaded gasoline versus premium usually saves about 20 cents per gallon or $7.50 per month.

Many people drive extra distance to find lower gas prices. Of course, the extra drive also means extra expense, so driving around to compare gas prices doesn't always make sense. Most of us drive past several gas stations in the course of our regular day, so finding the cheapest gas station on our route is certainly saves money, but what what happens to our costs when we drive out of our way for cheap gas?

If you have a 16-gallon gas tank, saving 5 cents saves you a maximum of 80 cents when you fill up (if you make sure to carefully arrive at the gas station completely out of gas). That 80 cents buys enough gas to drive about 7 miles (if gas is $2.25 per gallon and your car gets 22 mpg). Figure in the round trip (to and from the gas station) and you can drive 3.5 miles out of your way to save a nickel. Saving 10 cents allows you to drive about 7 miles out of your way and so on. So now you can evaluate that extra drive.

The most visible expense is not always the greatest expense. Now go and think mathematically.