First view here:
In 1919 a gallon of gas was $0.25, and in 2005 it was $2.84, which is a 1,036% increase.
Gas prices follow food/grocery prices (or vice versa) so it's reasonable to say one would need to increase their purchasing power the same amount to buy as much groceries from 1919 to 2005, as gas. So that's a 1,036% increase in purchasing power needed.
Now view here:
An ounce of gold was $19.95 in 1919 and $444.74 in 2005, which is a 2,217% increase.
Clearly gold kept up purchasing power.