One of the hottest topics of the summer has been the rising costs of oil, gas,and driving, in general. There's an entire movement growing around fuel efficiency and cutting back on driving costs. People talk of new concepts like "hypermilling" and old ones such as keeping your car's tires filled with air. The easiest, and least discussed, method to lower driving costs is to sell your car and stop driving!

For most, this would be too large an inconvenience to make a reality; however, what's more realistic is downgrading from multiple vehicles. If you are one of the countless Americans with more than one car, consider selling one. Whether or not you drive them, cars cost money.

The total cost of vehicle ownership is higher than most think. Besides pumping fuel for every inch of distance you drive, cars require continuous insurance payments and maintenence. Most importantly, cars come with a high opportunity cost on their value.

Opportunity cost is something we don't often consider when holding assets or buying things we don't really need. For instance, say that you have $15K in credit card debt with a 15% APR and just so happen to own a car that costs that much. Opportunity cost is the concept that if you hold the car you are stuck paying interest on that other debt, whereas if you sold it you could pay off the balance. In this case, it means you're paying roughly $185 per month on pure interest expense!

Adding insurance, gas, amortized maintenance costs, and opportunity cost of capital, the monthly cost of driving can easily reach $500 per vehicle. Selling a car could easily mean the difference between being under the water on your bills or financially solvent.