Although the most interesting method to save on car operating costs
> came from my chemistry teacher in high school (Buy your gasoline in
> the early morning or at night when it is cold outside. Gas becomes
> denser in cooler temperatures.
Did your teacher live in some hick town where they kept the 'gas' in tins?
In the UK by law it's kept in underground tanks. And any CSE grade student will know the temperature doesn't change there day by day.