I would not call less than a 10% increase astounding. Maybe over 15%, but not anything less than 10%. Our fleet increased about 7% between our 2017-2019 with a 6-speed versus the 2020-2021 trucks with a 10-speed. Even less of a difference for the trucks that are constantly loaded with a utility bed, cranes, and other equipment. Not too far off from Fuelly's numbers in regards to difference.
From our numbers, the only thing the 10-speed did is allow the PSD trucks to match the fuel mileage that the Cummins powered trucks in our fleet were already acheiving.