The Illinois gas tax is 48.3 cents per gallon of gasoline for the period running July 1, 2025, through June 30, 2026. That is only the state excise piece, though. Add the federal excise tax, two smaller state fees, the state sales tax that Illinois uniquely applies to fuel, and any county or municipal taxes, and the total tax on a single gallon of gasoline in Illinois lands somewhere between roughly 90 cents and well over a dollar depending on where you fill up.
The State Motor Fuel Tax Rate
Illinois charges a flat per-gallon excise tax that varies by fuel. From July 1, 2025, through June 30, 2026, the rates are:
- Gasoline and gasohol: $0.483 per gallon
- Diesel: $0.558 per gallon
- Liquefied petroleum gas: $0.558 per diesel gallon equivalent
- Liquefied natural gas: $0.558 per diesel gallon equivalent
- Compressed natural gas: $0.483 per gasoline gallon equivalent
Alternative fuels are measured by weight-based equivalents rather than liquid gallons because their energy density differs from conventional gasoline and diesel.1Illinois Department of Revenue. Motor Fuel Tax Rates and Fees
Two Small Per-Gallon Fees
Two additional charges apply on top of the motor fuel tax. The environmental impact fee is $0.008 per gallon, and the underground storage tank tax is $0.003 per gallon. Together they add just over a penny to each gallon.1Illinois Department of Revenue. Motor Fuel Tax Rates and Fees
Both fees apply to a broader set of petroleum products than the motor fuel tax itself. Home heating oil, kerosene, and aviation fuel are subject to the environmental impact fee and underground storage tank tax even though they escape the per-gallon motor fuel tax.2Illinois Department of Revenue. Motor Fuel Tax Definitions
Federal Excise Tax
The federal government adds 18.4 cents per gallon of gasoline and 24.4 cents per gallon of diesel. These rates have not changed since 1993 and are not indexed for inflation. A tenth of a cent per gallon goes to the Leaking Underground Storage Tank Trust Fund; the rest funds the Highway Trust Fund for federal road and transit projects.3Congressional Budget Office. Increase Excise Taxes on Motor Fuels and Index Them for Inflation
Sales Tax on Fuel
Illinois is one of the few states that charges general sales tax on gasoline, and the sales tax base includes the per-gallon excise taxes already built into the price. You are paying sales tax on top of other taxes. The state rate is 6.25%, and local jurisdictions can layer on their own sales taxes.4Illinois General Assembly. May 2025 Monthly Briefing – Taxes on Motor Fuel
Rather than collecting at the register, Illinois uses a prepaid sales tax system. The Department of Revenue sets a flat per-gallon rate twice a year, effective January 1 and July 1, based on the average selling price over the previous six months multiplied by 6.25%. For the period from January 1, 2026, through June 30, 2026, the prepaid rate is 17 cents per gallon for most motor fuels, 15 cents for gasohol (E15 blends), and 13 cents for mid-range ethanol blends. Distributors remit the tax, but the cost passes through to consumers.5Illinois Department of Revenue. Prepaid Sales Tax Rates
County and Municipal Fuel Taxes
Several counties impose their own per-gallon motor fuel taxes. In the Chicago collar counties, for the July 1, 2025, through June 30, 2026 period:
- DuPage County: 9.7 cents per gallon
- McHenry County: 8.5 cents per gallon
- Kane County: 5.0 cents per gallon
- Will County: 5.0 cents per gallon
- Lake County: 4.8 cents per gallon
Cook County and the City of Chicago impose separate per-gallon taxes under their home rule authority.6Illinois Department of Revenue. Change in the County Motor Fuel Tax Rate, Effective July 1, 2025 Municipalities throughout the state can also adopt their own, with some charging 2 to 5 cents per gallon on top of everything else.7Illinois Department of Revenue. FY 2026-09, Summary of Municipal Motor Fuel Tax Rate Changes
Filling up in downtown Chicago versus a rural station in southern Illinois can mean a 15-cent difference per gallon just from local taxes.
Total Tax on a Typical Gallon
Assume a base gasoline price of $3.00 at a station outside any county or municipal tax jurisdiction. The fixed per-gallon taxes look like this:
- Illinois motor fuel tax: $0.483
- Environmental impact fee: $0.008
- Underground storage tank tax: $0.003
- Federal excise tax: $0.184
- Fixed total: $0.678
The 6.25% state sales tax then applies to the combined base plus fixed taxes: 6.25% of $3.678 comes to about 23 cents. Total tax lands near 91 cents, pushing the pump price to roughly $3.91.1Illinois Department of Revenue. Motor Fuel Tax Rates and Fees
In a county or city with its own per-gallon tax and higher local sales taxes, the total climbs further. A DuPage County driver adds 9.7 cents in county motor fuel tax right off the top, and local sales taxes ride on top of the state rate. In the Chicago metro area, the combined tax burden on a gallon of gasoline can approach or exceed a dollar.
Why the Rate Rises Every July
Illinois law requires an automatic annual increase on July 1. The adjustment equals the percentage change in the Consumer Price Index for All Urban Consumers, measured by comparing the average CPI over the 12 months ending in March of the current year against the same period the year before. The result is rounded to the nearest tenth of a cent.8Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 505/2
Indexing lets the rate climb with inflation without a separate legislative vote each year. Illinois temporarily suspended the scheduled adjustment in 2022 as part of a broader relief package, but that was a one-time move. The automatic adjustment has resumed and applied each July since 2023.9Illinois Department of Revenue. FY 2025-23, Change in the Motor Fuel Tax Rate, Effective July 1
How Illinois Compares Nationally
Illinois sits well above the national average. As of January 1, 2026, the average state-level tax and fee on gasoline across the country was 33.3 cents per gallon. Illinois’s state motor fuel tax alone is 48.3 cents, roughly 45% higher than the national average before the additional Illinois-specific fees and sales tax layer.10U.S. Energy Information Administration (EIA). Many States Slightly Increased Their Taxes and Fees on Gasoline in the Past Year
State gasoline taxes range from 9.0 cents per gallon in Alaska to 70.9 cents per gallon in California. Illinois consistently ranks among the top five or six most expensive states for total gas taxes, partly because of the sales tax layer that most states do not apply to fuel, and partly because the annual CPI adjustment keeps ratcheting the base rate upward.10U.S. Energy Information Administration (EIA). Many States Slightly Increased Their Taxes and Fees on Gasoline in the Past Year
Who Does Not Pay the Illinois Motor Fuel Tax
Most drivers pay the full tax every fill-up, but a few categories of buyers can purchase fuel tax-free:
- Fuel sold to the federal government and its instrumentalities
- Fuel purchased by municipal corporations that own and operate local public transportation systems in Illinois
- Aviation gasoline (still subject to the environmental impact fee and underground storage tank tax)
- Dyed diesel delivered into stationary bulk storage or off-road equipment, provided highway vehicles cannot access it
- Motor fuel shipped to destinations outside Illinois
- Sales between licensed distributors or suppliers within the wholesale supply chain
Businesses that use fuel for off-highway purposes, such as construction equipment, farm machinery, or generators, may also claim a federal fuel tax credit on IRS Form 4136. The credit reimburses the 18.4-cent federal excise tax on gasoline or 24.3 cents on diesel used in qualifying non-highway business activities. Personal off-highway use, like lawn mowers and snowmobiles, does not qualify.12Internal Revenue Service. Instructions for Form 4136 and Schedule A