(18 Jul 2015, 7:33 pm)pdiddy wrote The e400mmc is a 6.7 litre Cummins unit
The StreetDecker is a 5.1 litre Merc/Daimler unit
Therefore the streetdecker has to be pushed much harder than the E400 therefore the engine would wear out much faster.
Would flogging a small engine be more economical than cruising with a big engine, I doubt it. And in the long term the e400mmc would surely more financially viable
It's not that simple.
You would have to look at the torque and the gearing (including the number of ratios) to compare performance.
Similar calculations for fuel consumption.
As long as a vehicle has the 'power' to meet the schedules it doesn't need extra - though it is useful to have some in reserve for delays and performance fall-off between services/repairs.
A more powerful engine needn't mean greater fuel consumption.