On June 2008, regular gasoline averaged $4.05 a gallon. In March 2022 dollars, that same price equals $5.27. The two numbers describe one moment, and the gap between them is inflation. A pump price is only half the story until you know which dollars it is stated in.
What the CPI measures when it tracks gasoline
The Consumer Price Index, or CPI, is produced by the U.S. Bureau of Labor Statistics (BLS). It measures what consumers pay for a broad set of goods and services. Gasoline is tracked as part of motor fuel inside that index. A move at the pump shows up as a measured price change, not as its own headline number.
BLS publishes a factsheet on how motor fuel price change is measured. It also has pages on average price data and on secondary source data for gasoline. The excerpts I reviewed were mostly navigation text. The method details are best read on the BLS site itself.
The index also draws on more than one kind of source. BLS has described its use of crowdsourced gasoline prices in a case study. How that data is checked and blended with other collection methods is not covered in the material available here.
Nominal prices versus inflation-adjusted prices
A pump price is nominal. It is the price on the sign at the time you fill up. A dollar in 2008 buys more than a dollar now, so the raw numbers do not line up. Think of a 2008 grocery receipt next to today's. The totals alone tell you little.
A price index is the usual fix. The adjusted figure is called the real price. It restates old prices in current purchasing power, so a comparison across years means something.
The Energy Information Administration (EIA) spells out its formula. Real price in a month equals the nominal price that month times the CPI in a base month divided by the CPI in that month. Every real price lands in the same base-period dollars.
EIA's March 2022 note shows the effect. Regular gasoline averaged $4.24 on March 21, 2022, after a peak of $4.32 on March 14. That was 22% above $3.53 on February 21. Yet in real terms, the 2008 price of $5.27 stayed the all-time high cited there. Compare nominal figures only, and you could draw a different conclusion.
Which price series a figure comes from
Several gasoline series exist, and they are built differently. The BLS CPI measures price change for motor fuel as one piece of a wide index. EIA's weekly retail series tracks the average price at the pump. EIA's real-price series then adjusts those nominal prices using CPI data.
The weekly series dates to August 1990 and updates each Monday. That makes it handy for short-term moves, month over month or week over week. EIA states that its retail prices include all taxes. Its weekly update showed a U.S. average of $4.153 a gallon, with a 2026 regional range from $3.578 in Texas to $6.031 in California.
That spread matters. A national average can sit far from the price on your corner. A news story that quotes one number should be traced to its series before you set it beside another. Mixing a CPI-based measure with a weekly average, or a nominal figure with a real one, gives a comparison that looks exact and is not.
Questions to ask before trusting a gasoline price comparison
Start with the dollars. Is the figure nominal or adjusted? If adjusted, which base month was used? The base changes the dollar values, so two adjusted figures only compare cleanly when they share one.
- Does the figure include taxes? EIA's retail prices do, and a price without them would run lower by an amount that varies by place.
- Which region does it describe? A state, a city, and the nation can all tell different stories.
- Which series is it? CPI, weekly retail, or real price.
There are gaps. The sources here do not explain how gasoline is weighted within the CPI. They also do not explain how gasoline moves headline versus core inflation, which is the version that leaves out food and energy. For those details, check the BLS methodology pages directly. For decisions about your own budget, a qualified professional can help. This article is educational only.
