Clark continues to receive many questions about the used Honda Civic GX he just purchased. Typically, a new GX runs about $25,000 versus $17,500 for a standard Civic. But some folks have been wondering if the extra investment is worth it. One boon to buyers is that you receive a $4,000 federal tax credit when you purchase this no-pollution natural-gas vehicle. Meanwhile, operating costs are about $1.20 per "gallon," though you don't fill up with traditional liquid gas. Clark instead uses compressed natural gas, which is largely produced here in the United States. He'll report back and let you all know if his GX purchase proves to be crazy or not. Meanwhile, the government has issued new fuel economy numbers for automobiles at FuelEconomy.gov. The push to get new numbers really gained momentum when people bought the Toyota Prius and found their sticker numbers could be inflated by 30 percent. But all 2008 vehicles going forward will feature the true miles per gallon figures. Note that you get greater value for your buck when you go from a vehicle that has 15 mpg to one that has 25 mpg -- rather than going from 25 mpg to 35 mpg. It's all about ratios. So it may make sense to buy a car with good mpg versus great mpg. It's that initial leap in fuel economy that gets you the biggest bang for your buck.