When I was learning how to drive, I was taught that air-conditioning was this enormous drag on gas mileage. I might as well be towing around an anvil behind the car. If I wanted better gas mileage I had to use the wind from the window.

Now it turns out that's not quite right. An air conditioner can up cut 2 mpg, according to American Petroleum Institute. But that's not nearly as much as the drag from your window will cut it. You're better off putting on the air at highway speeds, says the American Aftermarket Suppliers Association. According the the AAA, keeping windows closed at highway speeds can cut your fuel usage by 10%. But in stop and go traffic, you should keep your windows down and the air off.

Not everyone completely agrees. Edmunds did a study and found that on at least one pick-up, the Toyota Tundra, using the windows instead of the air improved gas mileage by nearly 10%. They chalked up the difference to the peculiarities of pick-up aerodynamics.

So, the old debate of windows or air can still be fought in car seats across the country. It sounds like the most economical solution is what people do just to enjoy the breeze but keep their hair from getting messed up: windows down at slow speeds, air conditioning on the highway.

Even though Fuelly seems to have too many vowels to be a web 2.0 application it has hit the ground running and provides users with a cool new way to track fuel usage. I had previously written about Fuel Frog, which lets you track your gas usage online at each fill up and it does a great job, but Fuelly really raised the bar. Fuelly has added a social aspect to tracking gas mileage by letting you compare your MPG with others driving your car and also with your friends and family to see who is getting the best mileage.

If you can get your friends to start using Fuelly then you'll have more of an incentive to track your gas mileage and be fuel efficient since we all seem to enjoy a little competition. You may find out some interesting stats about your friend's fuel usage while using Fuelly. While I have a fuel efficient car, I tend to drive like I'm trying to put out a fire somewhere while my friends with bigger vehicles are known to drive more like a 90 year old out for a Sunday drive. I can't wait to see who is getting more for their money.

I'm going to take Fuelly for a spin today when I fill up my car, I have fallen behind in my usage of Fuel Frog partly because I am lazy and partly because I couldn't remember the format for tracking it by text message. The competitive angle of Fuelly may be just what I need to stick with tracking my fuel cost and usage better and figuring out how to best budget for my gas needs. No matter how you track your gas consumption doing so is an easy way to empower yourself to watch your finances.



Hat tip to Lifehacker.

When I went to book a rental car for a family vacation up to the Adirondacks yesterday, I was surprised to find SUVs renting for less than small cars.

Last week ABC News had a story about how rental agencies were pressuring customers to take the SUVs off their lots. At an Avis in Manhattan, the midsize SUV is the cheapest vehicle available ($421 a week), followed by the standard SUV ($451), then the compact ($501). Oddly the biggest gas-guzzler, the full-sized SUV, is still the most expensive at $854 a week.

In other words, rental car prices have become even more irrational. That means if you're smart you may be able to get yourself a deal. I don't know the exact model they're offering (how many cylinders, etc.), but I could still take a guess at what the cost would be. A midsize SUV at Avis is the Pontiac Vibe, which according to carseek gets 26 mpg in the city and 33 mpg on the highway. That's pretty good mileage. The Vibe actually resembles your common station wagon. In fact, I bet Pontiac gets around to rebranding it that sometime soon.

The mid-sized SUV is a Chevy Trailblazer. We're moving into real SUV territory here. It only gets 16 mpg city / 22 mpg highway. The full-sized SUV is a GMC Acadia, which gets 17 mpg/city -- 26 mpg/highway.

Back to that compact car -- how does that do on gas? Avis uses a Chevy Cobalt. It only gets about 22/33. So, the Vibe SUV gets better mileage than the compact.

As gas prices rise, so will the importance of tracking gas purchases for your monthly budget. For some individuals tracking fuel purchases and performance is a simple exercise involving a notebook and a pen stashed in the center console. If division and receipt keeping aren't your style then I have a cool new tool for you! Fuel Frog is an online tracking service which measures not only your fuel costs but also your miles per gallon.

The service is easy to use and has a clean and user friendly online interface. Where it really shines though, is that it allows you to enter the information from your cell phone via Twitter. No more bundles of receipts or rushing to the PC as soon as you get home to record your fuel info. Its so simple you can do it in real time while you are waiting for your pay at the pump transaction to complete.

I have just started using Fuel Frog so I haven't had a chance to check out the monthly reporting yet but I expect it will come in very handy. At the least it will solidify my decision to carpool and encourage me to try and find more carpool partners. I am also a little bit scared to see how much I spend per month on gas. My only wish is that Fuel Frog offered a way to track two cars on one account so we could keep our house under one login, but two accounts will do in the meantime.