cooper1203:
Thanks for that i had a discustion with someone that should know a lot better about that very thing. he was insistant that i should never change gear when the engine was struggeling to the point you were nearly knocking hell out the bigends and shells he was aderment that mercedies knew what they were doing and if it needed to drop a cog or two it would.
For pretty much every lorry I’ve driven for the last 20 years they have a green band, yellow and red. Keep it in the green and it’ll give the best economy. In the yellow and red you’re just turning diesel into smoke. The lorries I drive, like virtually every lorry in the UK is an automatic, the green band goes all the way down to 800RPM and they won’t change down gear until they’re below 1000 RPM and they’ll change up a gear when it’ll drop the revs down to 1000 when you’ve changed up. Most of the torque is generated at the bottom end of the rev range and that’s what you need to keep the wheels turning. The most economical is where you’re in the rev range putting the most load on the engine which is at lower revs.
On the MAN you have a green band but there’s a portion of it which is a much more prominent green than the rest and it’ll move up and down depending on what you’re doing. Keeping the revs within this range is the absolute most economical. The dash below is from the same model as yours. It suggests you want to be keeping within 1100-2300RPM, ideally between 1300-1500 when cruising.
