Bought a new (well ok 10yr old but new to me) was only pulling 53mph on the limiter, aghhh soo slow, especially as I’ve never driven a limited truck, couldn’t find any tacho calibration stickers for a 6 or a 2 yr so sent it in for doing, result wayyhey 57 woo!
So you’ll save 4 minutes an hour which over a day isn’t enough to do a run but you’ll use more fuel and that’s apparently good?
Or is it that its actually not doing any more speed than it did but now the tacho is calibrated properly its showing what it did all along?
You need a set of special tacho calibration wheels. 
Bet it won`t pull up the hills any better,and will use more fuel in the bargain,costing more than you save in running time.
^^^^
Master class in bringing it down to earth. Excellent work.