The Roaring Twenties was a time of great economic prosperity in the United States which ended abruptly in the most severe economic collapse of the 20th century -- the Great Depression. While it lasted, however, goods that were previously reserved for the rich became more commonplace. One product growing in ownership was the automobile, which brought a whole new set of expenses to its owners, including gasoline, the price of which changed throughout the decade.
Gas Prices and Inflation
You can adjust the actual cost of gasoline to inflation and get an idea of what gas in the 20s cost in terms of today's dollars. According to the Energy Information Administration, the price of gasoline in 1920s dollars steadily fell from 30 cents in 1920 per gallon to 21 cents per gallon in 1929. Adjusted for inflation to today's dollar, the price of gas in the 1920s fell from $2.87 per gallon to $2.41, but the fall was much less steady, hitting a high of $2.90 in 1922 and a low of $2.34 in 1927.