The correct adjustment of roof air deflectors between tractors and trailers can save at least one percent on the fuel bill. To facilitate simpler adjustment, Scania has recently introduced an instrument panel switch for adjusting deflector height.  

　　“A mere six-centimetre incorrect height can result in one percent increased fuel consumption and with 10 centimetres wrong, the fuel penalty is 1.5 percent,” says Per Elofsson, Scania’s Senior Technical Manager for aerodynamics. 

　　Upon delivery from the dealer, the deflector is positioned considering the customer’s most common trailer height. The rule of thumb is to get the air flowing from the deflector slightly above the front edge of the trailer or bodywork. This is easier said than done and an optimal adjustment requires skilled calculations by the workshop.

　　However, when a tractor is coupled with a trailer that differs in height from normal, the driver can him- or herself make the adjustment by using the switch. By simply observing whether the trailer is higher or lower than normal, a slight adjustment can be made accordingly. As guidance, it is better that the deflector is a bit too high in relation to the trailer than vice-versa for better fuel performance.