From an email I received....

Here are some tricks to get more of your money's worth for every gallon.

Here at the _____ Pipeline where I work in CA we deliver about 4 million gallons in a 24-hour period thru the pipeline.

One day is diesel the next day is jet fuel, and gasoline, regular and
premium grades. We have 34-storage tanks here with a total capacity of
16,800,000 gallons.

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.

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. 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 other 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.

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.

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.