Teardrop trailers are the most aerodynamic shape -- but aerodynamics alone won't achieve fuel savings.

(Michael Westhoff/Getty Images)

Ask any long-haul trucker, one whose livelihood depends on squeezing every last mile from every last drop of diesel, and he'll tell you this: An aerodynamic trailer is more fuel-efficient and therefore cheaper to tow than a big, square box on wheels.

But the trucker has to overcome the unavoidable fact that his trailer is filled top to bottom and front to back with things like sacks of flour or boxes of concrete or enough kettle bells to supply every gym in Los Angeles. Aerodynamics for him include gap fairing, rear fairings and side skirts, all of which reduce the amount of turbulence and wind friction that keep the trailer from slipping along the highway like a greased eel. For a massive tractor-trailer owner, investing in these aerodynamic improvements can save something like 800 gallons (3,028 liters) of fuel each year -- enough for the average driver in San Jose, Calif., to tool around town for an entire year.

For those of us who sometimes take to the highways with a travel trailer hitched up behind a minivan full of sugar-happy kids on summer vacation, aerodynamics takes a completely different shape. Teardrop trailers, with the fat end right behind the car and the skinny end trailing away, are the most aerodynamic shape. If the top of the trailer is lower than the roofline of the vehicle towing it, that's even better. The air will flow over the roof of both objects and swirl off the back end. Most of these trailers are also lightweight, which means the engine of the towing vehicle doesn't have to work so hard to pull it. However, similar to the most efficient cars on the road, aerodynamics alone won't achieve fuel savings. It's a combination of shape, lightweight materials and clever design. Easy come, easy tow.

So why doesn't everyone tow a teardrop trailer? Apparently some people like to stand up. Even in the most cleverly designed teardrop, there's going to be some awkward space in the tail end. In a boxy travel trailer, you can usually walk front to back with only the merest whack of your forehead on the bunk bed someone forgot to put away that morning. In a teardrop trailer, no matter how long it seems from the outside, that back end is going to be sacrificed to storage or an exterior kitchen. Both are clever uses of space, but not places to stash kids for the night. Seriously. Don't put your kids in the exterior fold-out kitchen.