I've gotten Propane and Butane and that hide the facts LPG
type of stuff for 40+ years.

I used to have to get mine at a wholesale dealer - drive up the the pump
stand -
where the semi-trailer tankers get a drink themselves.

There they used a scale. Read the weight off the side and went from
there.
They hated the tiny bottles but heck - propane was their lives.
In the winter, when cold - they would just fill up to the overflow.

So I think it was a matter of safety. A hot day might outgass the tank
on
the way home.

Around here - always by the overflow - but then it is at a gas
station...

Propane by nature maintains a somewhat constant pressure within when not
frozen.
The gas expands and when the pressure builds up - it turns back into
liquid.

My brother-in-law used to work for Neptune and ? Gas Equipment - the
folks that
made the gas meters for propane.
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder