A route-determination method includes gathering road-related data in a vehicle navigation system (VNS) for a plurality of routes between two locations. This may include weighting two or more of the possible routes in the VNS based at least on the road-related data. Also, this may include adjusting the weighting in the VNS for each weighted route based on projected fuel consumption and determining an optimal fuel usage route in the VNS based on the adjusted weighting. Further, this may include outputting at least one optimal fuel usage route.