The one exception I've seen was a friend who had a long commute and drove a truck with a big V8. We did the math one day, and he could buy or lease a new Honda Fit and save more in gas than he would spend in car payments. I think he was getting <10 miles to the gallon, gas was $4.00 at the time, and he had a 40 mile commute each way.

His truck: 8 gallons/day X $4/gallon X 20 work days/month = $640/month on gas.

Fit(40 mpg): 2 gallons/day X $4/gallon X 20 work days/month = $160/month on gas.

Difference: $480/month.

Obviously, buying a used Fit or shortening his commute would save even more. He did shorten his commute a few years later.