What is the primary operational benefit of raising a liftable axle (aks me ngritje / lift axle) when driving a multi-axle truck in an unladen (empty) condition?

1. It allows the truck to carry double its gross legal payload capacity
2. It reduces tire rolling resistance, cuts tire wear, lowers fuel consumption, and reduces road toll charges where tolls are based on active road axles
3. It disables the service brake system for smoother coasting
4. It increases the vehicle's top speed beyond the speed limiter setting