Sometime in July, the federal government is going to launch a "cash for clunkers" program, paying new car buyers up to $4,500 to trade in a gas-guzzling older car for a new, more efficient vehicle. The stimulus-package program has been passed by Congress but is awaiting the president’s approval, and it’s geared to take older cars out of circulation and help boost sales of new cars.

We have a 1995 Ford Explorer that we’ve driven several sets of tires off during the past 14 years, so it qualifies for the maximum rebate amount, as long as I don’t buy a Hummer, I guess (and honestly, even the new Hummers gets better mileage than this Explorer). So my wife has reluctantly joined me as we’ve been trolling neighborhood car lots, looking at alternatives and trying to assess whether the incentive makes this a good time to buy or not.

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Anyway, here’s a quick way to find out how costly your driving habits are along with your car’s EPA mileage, cost to operate and carbon footprint: Check out this website, which lets you customize the parameters (miles driven each year, cost of gas, percentage of city vs. highway driving) and then compare what you have with virtually every car produced since 1985.

It’s not our official Friday productivity killer, but it’s not a bad way to kill a little time while learning a little more about your driving habits.