Ask The Expert - Money Saving Gas Tips - August 2011

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.
   
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 mode, 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.
 
One of the most important tips is to fill up when your gas tank is HALF FULL - 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. The less air in your tank means the less your gas is able to evaporate. Have you ever noticed how the last half of your tank seems to go by faster then the first half? The reason why is because more of your gas is evaporating away.

 
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, so it is better to be safe then sorry and fill up your car when the big storage tanks are NOT being refilled.