Illinois vs Indiana gas prices
Regular gas is $0.73 a gallon cheaper in Indiana — $10.95 on a 15-gallon fill-up. The two share a border, so that gap is worth knowing before you cross it.
Illinois
Indiana| Grade | IL | IN | Diff. | |
|---|---|---|---|---|
| Regular | $4.35 | $3.62 | $0.73IN | Indiana |
| Midgrade | $4.94 | $4.19 | $0.74IN | Indiana |
| Premium | $5.46 | $4.72 | $0.74IN | Indiana |
| Diesel | $5.32 | $5.36 | $0.04IL | Illinois |
Where the $0.73 gap actually comes from
15% of it is tax. Illinois charges $0.11 more per gallon in federal and state taxes than Indiana. The remaining $0.62 is a real difference in what the fuel, refining and distribution cost — refinery proximity, pipeline access and state fuel-blend rules.
Fuel, refining, distribution and marginFederal and state taxes Local county and city fuel taxes are not included, and Illinois permit them. Pre-tax figures are estimates — see the note below.
What the gap is worth
Based on today’s $0.73 per-gallon difference, which moves week to week. Use the fuel cost calculator for your own mileage and vehicle.
Prices by metro area
State averages hide a lot. These are the cheapest metros AAA reports on each side.
Other comparisons
Frequently asked questions
Is gas cheaper in Illinois or Indiana?
Regular gas is cheaper in Indiana, at $3.62 a gallon against $4.35 in Illinois — a gap of $0.73, or 20.2%. On a 15-gallon fill-up that is $10.95. Figures are AAA daily state averages for 2026-08-02.
Why is gas more expensive in Illinois?
15% of the $0.73 gap is tax rather than the cost of the fuel. Illinois levies $0.11 more per gallon in federal and state taxes; the remaining $0.62 is a genuine difference in what the fuel, refining and distribution cost.
Is diesel cheaper in Illinois or Indiana?
Diesel is cheaper in Illinois at $5.32 a gallon, against $5.36 in Indiana — $0.04 a gallon apart. Note that this is the opposite way round from regular gas, because the two states tax the two fuels differently.
Is it worth crossing from Illinois into Indiana to fill up?
If you are already near the line, yes: a 15-gallon fill saves about $10.95. Driving out of your way for it rarely pays — at $4.35 a gallon and 25 mpg, a 31-mile round trip would eat the whole saving in fuel alone, before your time.