[ankit]

I haven't heard too much of people trading in their trucks for new vehicles. But, I have heard of some buying beaters that get good FE such as a Civic and then making up the money they paid for it in savings of gas bills.

As for an exhaust system, it could be more of an enthusiast thing with the extra benefit of good FE. "Hey, I've wanted a nice throaty exhaust system for a while now. I know it will eventually pay for itself (in about 2-3 years of driving*) and I get to add something to my mod list." This is especially worth it if the stock exhaust is not doing its job anymore and needs replacement anyways.

Although, I do agree that buying a new car or tons of money into the existing car just for FE is not a good investment.

*12,000 miles/year
previous FE: 22 MPG
after exaust: 24 MPG
$4.00/gallon of fuel
$500 cat-back exhaust
______________________

2.77 Years till payoff and "X" years of deep throaty driving fun.