I stumbled upon a fascinating post in The Daily Score this morning. It's premise: You save more fuel switching from a 15 to 18 mpg car than switching from a 50 to 100 mpg car.

At last, I may have found a way to overcome the uncertainty and indecision over which vehicle to buy next. (Since I haven't heard of any new cars on the drawing boards that fit my needs, I'm assuming I'll have to endure one more 2-3 year cycle of a less than perfect vehicle to meet our lifestyle needs.)

Of course, there aren't any 100 mpg cars to switch to, but all year long, my Prius owning friends have been trying to get me to make the leap from an Audi A4 Avant to a Prius. According to the EPA that would be a switch from 26 mpg highway to 45 mpg highway (I use highway estimates because we live in a small town and take a lot of road trips).

But, here's one wrinkle: of the 9700 highway miles we drove this year, 8200 of them were with 2-3 bikes in the roof rack. The net effect = 16-18 mpg, rather than 26. Another wrinkle: my interest in moving the bikes inside a new vehicle, rather than onto another mpg compromising bike rack — even if it's hanging off the back of a Prius.

So, I'm back to comparing the Audi A4 Avant with a Honda Element 4WD. The question: how much gas would I have saved by driving 8200 miles with the bikes inside an Element (24 highway mpg) vs on top of our Audi (16 mpg)? Thanks to Eric De Place's spreadsheet on The Daily Score, here are the numbers:

Audi A4 Avant: 8200 miles at 16 mpg used 497 gallons of gas (premium)
Honda Element 4WD: 8200 miles at 24 mpg would only have used 331 gallons of gas (regular)

I could have used 166 fewer gallons of fuel (33%) by driving a Honda Element.

With the price of premium gas being at least 25 cents higher than regular, on average, the cost savings in this hypothetical exercise would have been about $600.

So, what am I waiting for? The perfect car, of course. In the meantime, I may finally be convinced that it's OK to switch to a Honda Element.

Carbon Neutral Journal's stats are brought to you by Blue Spruce Cleaners.