Volvo VNL 780 Operator's Manual page 306

296 OPERATION
Tires
Heavy duty threaded tires increase rolling resistance considerably. For long haul, choose
a smoother, ribbed type tire. Choose a lugged type tire only when the added traction in
mud and snow is needed.
The number of wheels (axles) has a direct effect on the rolling resistance and, thereby, the
fuel consumption. For volume and/or low weight transports, the use of a 4x2 instead of a
6x4 should be considered.
If the tire pressure is too low, the rolling resistance increases and, thereby, increases the fuel
consumption. The overall economy is also affected as tire wear increases considerably.
Gross Vehicle Weight
The gross vehicle weight of a vehicle combination has a large impact on the rolling
resistance.
Accessories
As a rule, accessories such as roof rack, advertising signs, bug screens, exposed air horns,
etc., have a negative effect on fuel consumption.
Service and Maintenance
A modern heavy-duty vehicle requires regular and preventive maintenance to ensure that all
its components function as they should. Use the recommended preventive maintenance (PM)
program that Volvo Trucks North America has developed for the vehicles. This ensures
optimal energy efficiency from all components that are important to fuel consumption.