When it comes to aerodynamic versus traditionally-styled sleeper tractors, owner-operator trucks are still commanding a premium in the used-truck market despite the importance of fuel economy, according toa blog post by the National Automobile Dealer Association.

According to NADA's research, the average owner-operator truck sitting on a dealer's lot is slightly older and has higher mileage than its aerodynamic counterpart, according to Chris Visser, senior analyst with the American Truck Dealers/NADA Official Commercial Truck Guide. However, so far in 2012, the cost of traditional sleeper tractors has averaged more than $4,000 higher than aerodynamic trucks after adjusting for specs.

There was a price decline from September 2011 to March 2012, caused by corresponding increases in average mileage and age. That trend reversed for April.

Visser says the appeal likely comes from the increased versatility of a traditionally styled truck, including features such as a removable sleeper and set-forward axle. Also, the supply of these trucks is much smaller -- NADA says its database of owner-operator sleeper tractors is only 12% the size of its aerodynamic database. Condition is also a possible factor.

"If owner-operator trucks have not given back any of their price premium at this point, we do not expect them to going forward," Visser says. "Buyers are under no illusions about the future price of fuel, so current values have those assumptions priced in."