My own info on the Volvo B7tl appears to indicate an average of 6mpg in City
Service.
The Trident using a somewhat larger Cummins power unit may well be slightly
better as in our service the smaller engined B7`s are constantly being
thrashed especially when loaded.
I would like to get accurate figures for the Marshall spec Cummins/Allison
combination but I would be wary of any of the "Official" TfL ones as I
should imagine any figure which would show a good average might have to be
"Amended".......Conspiracy Theory.....You Bet.!