$0 for gas is not true here, but the real consumer issue is that the difference in the weekly gas price among competitive models rarely comes close to being a significant factor when compared to the affects of chargable options at sale time. If I find a new car that will increase my mileage by 50% and save me $30 per week, I'm still better off keeping my old car that is paid off instead of having a car payment that will be far more than $120/month.

The class of vehicle and the market price are the true factors that affect overall cost the most. If you buy a compact instead of an SUV, you will save money. But it's not just the gas. It's the overall cost that will be much lower. Unless you get an expensive hybrid, in which case the premium that you pay for the vehicle will offset the savings in gas in many cases, compared to an inexpensive compact driven moderate distances.