The little bit I've talked to people about propane in systems like these, a lot of times the gauges leave something to be desired....
Resolution/accuracy is limited. The gauge in my buddy's old ex-highway dual-fuel F150 only had about 4 LED's on it. He liked it as a fuel option (and his natgas one that got taken out by a falling tree, even better), but you'd have to be wary of that gauge if it was your only fuel source.
UPS up here runs a lot of propane local trucks...... our regular driver at work came in really late one day to drop a package.
His truck had a non-working gauge, and said a lot of the local fleet was the same. Not that big a deal for a local route, EXCEPT that the night-service guy didn't propane-up the truck in their shop, as he is supposed to do
every night.
He spent a while on the side of the road that day........ portable propane fillups are harder to execute than gasoline or dzl.....
Accurate Tare Weight measurements on mobile equipment tanks should be do-able...... just likely not at the price-point that 100 years of liquid fuel-float production has gotten down to.
I like that Ford still offers a gaseous fuel-prep package (last I checked) on their SuperDuty line. If you like to drive long distances (I do still), the original gas tank + a large size CNG or propane tank will give some serious range between fillups..... on my
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Rgds, D.