With the price of gasoline (between about $3.30 and $3.80 here in Southern California for unleaded regular - higher grades are well over $4 per gallon) hurting almost every budget, this advice from an email corespondent in the fuel biz about how to get the most at the pump is both timely and welcome.
... my line of work is in petroleum for about 31 years now, so
here are some tricks to get more of your money's worth for every
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. And 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. ALL gasoline stations must have "in-line"
fuel filters....But, 'HOW OFTEN' they replace them is another
story, so wait 25 minutes after a gas delivery, OR go to another