Tips on pumping gas

I read the article here by a guy whose line of work is in petroleum.

1. Only buy or fill up your car or truck in the early morning when the
ground temperature is still cold. Remember that all service stations have
their storage tanks buried below ground. The colder the ground the more dense
the gasoline, when it gets warmer gasoline expands, so buying in the
afternoon or in the evening....your gallon is not exactly a gallon. In the
petroleum business, the specific gravity and the temperature of the gasoline,
diesel and jet fuel, ethanol and other petroleum products plays an important role.

A 1-degree rise in temperature is a big deal for this business. But the
service stations do not have temperature compensation at the pumps.

2. When you're filling up do not squeeze the trigger of the nozzle to a
fast mode. If you look you will see that the trigger has three (3) stages:
low, middle, and high. In slow mode you should be pumping on low speed,
thereby minimizing the vapors that are created while you are pumping. All hoses
at the pump have a vapor return. If you are pumping on the fast rate, some
of the liquid that goes to your tank becomes vapor. Those vapors are being
sucked up and back into the underground storage tank so you're getting
less worth for your money.

3. One of the most important tips is to fill up when your gas tank is HALF
FULL or HALF EMPTY. The reason for this is, the more gas you have in
your tank the less air occupying its empty space. Gasoline evaporates faster
than you can imagine. Gasoline storage tanks have an internal floating
roof. This roof serves as zero clearance between the gas and the
atmosphere, so it minimizes the evaporation. Unlike service stations,
here where I work, every truck that we load is temperature compensated so
that every gallon is actually the exact amount.

4. Another reminder, if there is a gasoline truck pumping into the storage
tanks when you stop to buy gas, DO NOT fill up--most likely the
gasoline is being stirred up as the gas is being delivered, and you might pick up
some of the dirt that normally settles on the bottom.

Hope this will help you get the most value for your money.