Why is gas expensive in Illinois?
Illinois drivers pay $3.59 per gallon, about 21 cents above the national average. The state has the country's highest combined state and local gas tax — about 78 cents per gallon — and the Chicago metropolitan area falls under federal Reformulated Gasoline rules. Illinois drivers pay more than residents of every state except California, Hawaii, Washington, Oregon, and a handful of West Coast states.
What you're paying for
State taxes and policy in Illinois add an estimated $0.86 per gallon on top of the roughly $2.73 base cost (crude oil, distribution, and the federal excise tax) that every U.S. driver pays.
Against its neighbors
Amber line marks the U.S. average of $3.38.
Price over time
Illinois U.S. average
Illinois, explained
Why does Illinois have the highest gas tax in the country?−
Illinois combines three layers of state and local fuel taxation: the state excise tax of 47 cents per gallon, the regular state sales tax of 6.25% applied to motor fuel (adding about 20 cents per gallon at current prices), and additional municipal and county taxes in the Chicago area (11 cents combined). Together, these layers total about 78 cents per gallon, the highest combined state and local burden in the United States.
Is the Illinois gas tax indexed to inflation?+
Yes. Since the 2019 Rebuild Illinois capital plan doubled the state excise tax from 19 to 38 cents per gallon, the tax has been indexed to inflation and adjusted automatically each July 1. The 2026 rate is 47.0 cents per gallon. Indexing means the tax rises every year without legislative action.
Why is gas more expensive in Chicago than the rest of Illinois?+
Chicago and Cook County add their own fuel taxes on top of state taxes. Chicago's tax is 8 cents per gallon, plus a Cook County tax of 6 cents per gallon, plus the Regional Transportation Authority's 1.25% sales tax on motor fuel. Combined with the federal Reformulated Gasoline requirement for the Chicago metro area, drivers in Chicago pay roughly 25 cents per gallon more than drivers in southern Illinois or central Illinois counties outside the RFG area.
Why are Illinois refineries not lowering prices?+
Illinois has four operating refineries (BP Whiting, ExxonMobil Joliet, Marathon Robinson, Citgo Lemont). Combined capacity is about 950,000 barrels per day, significant by national standards. But refinery proximity does not lower retail prices because gasoline is sold at wholesale spot prices set in regional markets. Refinery-state status does not, in our regression, lower a state's retail price after taxes and other policy factors are accounted for.
Does Illinois have a low-carbon fuel standard?+
Not yet. A Clean Transportation Standard, modeled on California's LCFS, has been proposed in the Illinois General Assembly multiple times but has not passed. If enacted, our model projects a price effect of 15 to 25 cents per gallon based on the experience of California, Oregon, and Washington.
How does the Illinois Motor Fuel Tax indexation work?+
Under the 2019 law, the state excise tax is adjusted each July 1 by the change in the Consumer Price Index over the prior year. The tax has risen every year since indexation began: from 38.0 cents in 2019 to 47.0 cents in 2026, a 24% increase. Indexation produces an automatic tax increase without a legislative vote each year.