I drove my car until it was on fumes. Then I fueled it up. My car has a 12 gallon tank, and i usually get 300 miles out of it (that's 25mpg). At $4.00/gallon for gas, that's $48 to fill up the tank.

Flash forward to about two weeks later. My car is on fumes again and guess what - the trip meter was showing 330 miles. Which means i got a 10% increase in gas mileage. That's 27mpg. Or another way to look at it is that at $4.00/gallon, i just saved $0.40 per gallon of gas, effectively giving me me gas at $3.60.

Let's look at it another way. I drive approxmiately 20 miles each way to work, or 40 miles round trip. Assume that i drive in to work around 200 days a year (sounds about right after you factor in weekends, holidays, working from home, etc..). That's 8000 miles. At $4.00/gallon on my old gas mileage (25mpg), that would be 320 gallons of gas, or $1,280. Assuming the new gas mileage (27mpg), that would be 296 gallons of gas, or $1,184. Giving me a total savings of: $96.00.

So the question becomes: Is it worth it for me to drive agonizingly slow every day, adding about 5 minutes to my commute each way in order to save $100/year?