When Was Gasoline Most Expensive? The table below includes data on the average retail price of a gallon of unleaded gasoline from 1976 to 2004. Use the data on the CPI for each year to adjust the price of gasoline to see when gasoline was most expensive relative to the price of other goods as measured by the CPI. For each year you will need to divide the price of gasoline by the CPI and then multiply by 100. While 2003 and 2004 show some of the highest nominal prices, when was the relative price of gasoline the highest? Was it 2003 or 2004