there is no lmpg display in the HAH...tripA/B only. Since I don't have navi, A keeps my tank average, reset every fillup, B gives me that day's (actually that commute segment), reset each trip.

Seems like you'd need to get either a very naive owner who doesn't know about trip B, or one who is on their honor to have never reset it/ kept true records for every tank.

Do you guys all have another mode buried in the navi?