Iowa vs South Dakota gas prices
Regular gas is $0.07 a gallon cheaper in Iowa — $0.98 on a 15-gallon fill-up. The two share a border, so that gap is worth knowing before you cross it.
Iowa
South Dakota| Grade | IA | SD | Diff. | |
|---|---|---|---|---|
| Regular | $4.11 | $4.17 | $0.07IA | Iowa |
| Midgrade | $4.37 | $4.41 | $0.04IA | Iowa |
| Premium | $4.95 | $4.93 | $0.02SD | South Dakota |
| Diesel | $6.12 | $5.99 | $0.13SD | South Dakota |
Is cheaper gas worth the detour?
Use your tank and extra travel costs. Prices below are AAA state averages as of 2026-09-16; check the actual station prices before driving.
Extra distance and time include the return to your original route. Detour fuel uses the higher state price. Tire wear and maintenance are excluded. This estimates a price difference; it does not verify a station offer or route.
Where the $0.07 gap actually comes from
None of it is tax. This is the case people assume never happens: South Dakota is dearer at the pump while taxing a gallon $0.01 less than Iowa. The whole gap is the cost of the fuel itself — refinery proximity, pipeline access and state blend rules — and the tax difference is quietly shrinking it.
Fuel, refining, distribution and marginFederal and state taxes Pre-tax figures are estimates — see the note below.
What the gap is worth
Based on today’s $0.07 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 Iowa or South Dakota?
Regular gas is cheaper in Iowa, at $4.11 a gallon against $4.17 in South Dakota — a gap of $0.07, or 1.6%. On a 15-gallon fill-up that is $0.98. Figures are AAA daily state averages for 2026-09-16.
Why is gas more expensive in South Dakota?
Not because of tax — South Dakota actually levies $0.01 a gallon less than Iowa. The whole $0.07 gap, and more, is the cost of the fuel itself: refinery proximity, pipeline access and state fuel-blend rules. Tax policy is narrowing this gap rather than causing it.
Is diesel cheaper in Iowa or South Dakota?
Diesel is cheaper in South Dakota at $5.99 a gallon, against $6.12 in Iowa — $0.13 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 South Dakota into Iowa to fill up?
If you are already near the line, yes: a 15-gallon fill saves about $0.98. Driving out of your way for it rarely pays — at $4.17 a gallon and 25 mpg, a 3-mile round trip would eat the whole saving in fuel alone, before your time.
Why this price is what it is
- Premium vs. Regular Gas: Is Premium Actually Worth It?Premium costs more per gallon — but does it help your car? Here's when premium is worth it, when it's wasted money, and what octane really does.
- Fuel Taxes Explained: What You Really Pay Per GallonA big slice of every gallon is tax — but how much, and where does it go? A clear guide to federal, state and European fuel taxes.
- The Best Day and Time to Buy Gas (Backed by Price Data)Studies of billions of transactions point to early in the week as the cheapest time to fill up. Here's the best day, the best time of day, and why it works.