Gas Prices in St. Louis: Why Illinois Costs More, and the Missouri Refund Almost Nobody Claims
Revised August 16, 2026
Why is gas so much higher in Illinois than Missouri?
Taxes, almost entirely. Per the Tax Foundation, Illinois carried 66.4 cents a gallon in combined state taxes and fees as of July 2025, second-highest in the country, against Missouri’s 29.99 cents. Illinois also applies its 6.25% general sales tax to motor fuel, calculated on a price that already includes the excise, so the Illinois tax bill climbs whenever crude does. Missouri’s does not.
Keep reading ↓Imagine it’s a Tuesday evening and the low-fuel light blinks on somewhere around Maryland Heights. Forty miles of range left, and a fuzzy memory of what the sign said this morning. No crisis. Just the small arithmetic every driver here runs without noticing.
Maybe you live in Belleville and have quietly gotten into the habit of topping off on the Missouri side before you head home. Maybe you live in Kirkwood and have never thought about it, because you don’t cross the river on a weeknight. Same car, same tank, two different bills.
That gap isn’t a rumor, and it isn’t the station owner being greedy. It is written into two state tax codes that treat a gallon of gasoline in completely different ways — and one of those states will send part of it back to you, if you ask before September 30.
Why is Missouri gas so cheap, and Illinois gas so expensive?
Because Illinois taxes fuel far more heavily. Current gas prices in Illinois show it plainly: on August 15, 2026, AAA put regular unleaded at $3.83 in the Missouri half of the St. Louis market and $4.27 in the Illinois half, which AAA reports as East St. Louis. That is a 44-cent spread on the same commodity, ten minutes apart.
The Tax Foundation’s July 2025 state gas tax tally explains almost all of it. Illinois came in at 66.4 cents a gallon in combined state taxes and fees, second-highest in the country behind California. Missouri came in at 29.99 cents, ranked 28th. That is a 36-cent structural gap before a single station sets a price.
Are taxes higher in Missouri or Illinois on a gallon of gas?
Missouri charges a flat excise tax of 29.5 cents per gallon, plus two small fees: an agriculture inspection fee of about 0.09 cents and a transport load fee of 0.4 cents. Missouri then stops. Under state law, motor fuel already subject to the fuel excise is exempt from Missouri sales tax, so nothing gets stacked on top.
Illinois runs a different machine. Its motor fuel tax on gasoline and gasohol sits at 48.3 cents a gallon for July 1 through December 31, 2026, per the Illinois Department of Revenue. Add a 0.8-cent environmental impact fee and a 0.3-cent underground storage tank tax. Then — and this is the part that stings — Illinois also applies its 6.25% general sales tax to motor fuel, calculated on a price that already includes the excise taxes. When crude climbs, the Illinois tax bill climbs with it. Missouri’s doesn’t.
One thing Metro East drivers often get wrong: there is no county fuel tax over here. Illinois authorizes a county motor fuel tax of 4 to 8 cents a gallon only in DuPage, Kane, Lake, McHenry and Will. Madison, St. Clair and Monroe are not on that list. The federal tax is identical on both banks, so it cancels out of the comparison.
How much does crossing the river actually save you?
On the August 15, 2026 numbers, a 15-gallon fill costs about $6.65 less on the Missouri side. Burn 500 gallons a year and the gap is roughly $222. Real money — but only if the trip is one you were making anyway.
Here is the honest counterweight. Driving 12 extra miles round-trip to save $6.65 hands most of it back in fuel, wear and half an hour of your evening. The savings are real for anyone already crossing the Poplar Street or the Blanchette. If you work in Clayton and live in Edwardsville, fill up on the way home. If you never leave St. Charles County, this is a fun fact, not a strategy.
How do I claim Missouri’s 12.5-cent gas tax refund?
File Form 4923-H with the Missouri Department of Revenue between July 1 and September 30, 2026, for gas you bought between July 1, 2025 and June 30, 2026. The refund is 12.5 cents per gallon — the entire increase Missouri phased in since 2021 — on any vehicle rated 26,000 pounds or less. That window is open right now.
Missouri’s fuel tax climbed 2.5 cents every July from 17 cents in 2021 to 29.5 cents on July 1, 2025, where it stopped. The legislature attached a refund to the increase for ordinary passenger vehicles, and the Department of Revenue’s motor fuel FAQ lays out the rules: claims must be postmarked on or after July 1 and no later than September 30 following the fiscal year, and you keep the original receipts for three years after filing.
The paperwork is why most people skip it. For every purchase you need the date, the number of gallons, the name and address of the seller, and the VIN of the vehicle you put it in — a separate worksheet per vehicle. Loyalty account statements from a fuel program count if they carry that detail, which is the single best reason to run every fill-up through one card or one app. You can file it online through MyTax Missouri rather than mailing a shoebox.
Almost nobody does. Reporting from July 2026 put the average refund paid in 2025 at $162.74, with about $2 million distributed statewide. Claim counts ran 15,000 in 2022, 10,820 in 2023 and 11,801 in 2024 — against more than 4 million Missouri drivers. Under 1% file. Run your own math rather than anchoring on that average: 500 gallons times 12.5 cents is $62.50, and a two-car household burning 1,000 is looking at $125.
Wildly off-topic — the cheap fill-up matters less than a good auto repair shop.
Did Missouri just put a sales tax on gasoline?
No. On August 4, 2026, Missouri voters rejected Amendment 5 by roughly 82% to 18%. The measure would have phased out the state income tax and let the legislature extend sales tax to goods and services it currently cannot reach — motor fuel among them, which would have been a first for Missouri.
It failed decisively, so Missouri still collects a per-gallon excise and no sales tax on gasoline. Keep that in mind the next time a fuel-tax headline goes by: the per-gallon rate and the sales-tax question are two separate levers, and only Illinois currently pulls both.
Is premium gas worth it if your car doesn’t require it?
If your owner’s manual says regular, premium buys you nothing. AAA tested this and found no significant benefit in horsepower, fuel economy, emissions or engine cleanliness from running premium in a car designed for 87 octane. AAA estimated Americans waste $2.1 billion a year doing it, with 16.5 million drivers buying premium their manufacturer never asked for.
The nuance is in the word your manual uses. Required means required — buy the premium. Recommended is different, and AAA ran a second study on exactly those vehicles. Under demanding conditions like towing, hauling and hard acceleration, they averaged 2.7% better fuel economy and 1.4% more horsepower on premium. In ordinary city and highway driving, AAA found those cars unlikely to show any benefit at all. Towing a boat to Carlyle Lake in August is the case for premium. Sitting on I-64 is not.
Does TOP TIER gas actually make a difference?
Yes, and the margin is not subtle. AAA’s testing found non-TOP TIER gasoline left 660 milligrams of deposits per intake valve after 4,000 miles of simulated driving, versus an average of 34 milligrams for TOP TIER fuels — 19 times more. Switching to TOP TIER cut existing intake valve deposits by 45% to 72% over 5,000 miles.
TOP TIER is not a brand or an octane grade. It is a detergent standard automakers created in 2004 because the EPA minimum was set lower than they wanted, and it is now sponsored by BMW, General Motors, Ford, Stellantis, Honda, Toyota, Volkswagen, Mercedes-Benz, Audi and others. More than 100 retail brands are licensed in the US, and it applies to every octane grade sold at a licensed site, decal on the pump or not. It costs nothing extra. Cheapest maintenance decision on the list.
What is Unleaded 88, and can your car use it?
Unleaded 88 is E15 — 15% ethanol instead of the 10% in ordinary regular. The EPA has approved it for 2001 and newer cars, trucks and SUVs. It is not approved for anything older, and it is not approved for motorcycles, boats, lawn equipment or any other small engine. It usually prices a few cents under regular.
Ethanol is already in nearly every gallon sold in Missouri. The Missouri Renewable Fuel Standard Act requires retail gasoline to contain 10% ethanol, with carve-outs for premium grades, aviation fuel, and cases where a distributor can’t source blended fuel at or below the price of unblended. Ethanol carries less energy per gallon than gasoline, so a higher blend gives up a little mileage. That is the real question when Unleaded 88 sits a nickel under regular: sometimes that nickel is a discount, sometimes it is a wash.
What a fill-up looks like from behind the counter
The pump is not where the money is. About 80% of America’s fuel is bought at convenience stores, and roughly 55% of fuel-selling stores are single-store operators — one family, one site, per NACS. Fuel margins averaged just over 40 cents a gallon in 2025, gross, before rent, labor, insurance and cards. The industry paid a record $21.3 billion in swipe fees that year, $4.6 billion of it charged on the taxes retailers collect and hand to the state — paying a card network a cut of Illinois’ 48.3 cents is the complaint you hear at any jobber meeting. Inside sales hit $341.2 billion: the coffee and the roller grill carry the site, and the sign out front just gets people to the door. Branded operators are usually independents on a supply agreement, often a 10-year term with volume and image standards, while unbranded sites shop the open rack. If you run one, being listed and complete on St Louis Near Me Directory is how the driver searching at 10 p.m. finds your canopy.
Related reading: what salt season does to your car and the corner store math on everything else.
Which two stations do you actually drive past every day? Browse gas stations across the St. Louis metro on St Louis Near Me Directory, then confirm your regular stop carries a TOP TIER brand before the next fill-up — and start saving receipts, because next year’s refund window opens July 1.
Frequently asked questions
What are the current gas prices in Illinois?
AAA put regular unleaded at $4.27 a gallon on August 15, 2026 in the area it reports as East St. Louis. Missouri-side stations averaged $3.83 the same morning — a 44-cent spread ten minutes apart. Pump prices move daily, so read that as the shape of the gap, not today’s number.
Why is gas so much higher in Illinois than Missouri?
Taxes, almost entirely. Per the Tax Foundation, Illinois carried 66.4 cents a gallon in combined state taxes and fees as of July 2025, second-highest in the country, against Missouri’s 29.99 cents. Illinois also applies its 6.25% general sales tax to motor fuel, calculated on a price that already includes the excise, so the Illinois tax bill climbs whenever crude does. Missouri’s does not.
Why is Missouri gas so cheap?
Missouri charges a flat 29.5 cents a gallon plus two fees under half a cent combined, and then stops. State law exempts motor fuel from general sales tax, so nothing stacks on top, and voters rejected Amendment 5 on August 4, 2026, which would have let the legislature change that. Drivers who file Form 4923-H get 12.5 cents a gallon back.
Are taxes higher in MO or IL?
On motor fuel, decisively Illinois: 66.4 cents a gallon in combined state taxes and fees against Missouri’s 29.99 cents, plus a 6.25% sales tax Missouri does not charge on gasoline. That is one line item, not the whole code — income and property taxes are a separate question.
How much is the Illinois gas tax per gallon right now?
48.3 cents per gallon on gasoline and gasohol from July 1 through December 31, 2026. Illinois normally raises the rate every July using an inflation formula, but Public Act 104-0468, signed June 16, 2026, suspended that adjustment for six months. Add a 0.8-cent environmental impact fee, a 0.3-cent underground storage tank tax, and the state’s 6.25% sales tax on top of the pump price.
How do I get money back from the Missouri gas tax?
Submit Form 4923-H to the Missouri Department of Revenue, on paper or through MyTax Missouri, between July 1 and September 30 for the fiscal year that ended June 30. You claim 12.5 cents per gallon on vehicles rated 26,000 pounds or less. Each purchase needs a date, gallon count, seller name and address, and the vehicle’s VIN. Hold the original receipts for three years after you file.
Is it worth driving across the river for cheaper gas?
Only if you were already going. A 15-gallon fill at the August 15, 2026 spread saves about $6.65, roughly $222 a year at 500 gallons. Make a dedicated round trip and the extra miles, wear and time eat most of that. Commuters already crossing the Poplar Street or the Blanchette should just time the fill-up.
Does premium gas give you better gas mileage?
Not in a car built for regular. AAA’s lab testing found no meaningful gain in fuel economy, horsepower, emissions or engine cleanliness, and pegged the national waste at $2.1 billion a year. In vehicles where the manual says premium is recommended rather than required, AAA measured about 2.7% better economy and 1.4% more power — but only under towing, hauling or hard acceleration, not normal driving.
Is TOP TIER gas worth paying more for?
It generally isn’t more expensive, which is what makes it easy. AAA found non-TOP TIER fuel left 660 milligrams of deposits per intake valve after 4,000 test miles against 34 milligrams for TOP TIER, and switching cut existing deposits 45% to 72% over 5,000 miles. Over 100 US retail brands are licensed, and the standard covers every octane grade sold at those sites.
Can my car run on Unleaded 88 or E15?
If it is a 2001 or newer car, truck or SUV, the EPA says yes. Anything built in 2000 or earlier is out, as are motorcycles, boats and small engines like mowers and generators. E15 holds 15% ethanol against the 10% in standard regular, so expect a slight mileage trade for the lower price. Check the pump label and your owner’s manual before the first fill.
Written by a dedicated team of St. Louis locals who live, work, and play right here in the St. Louis metro. Founder Lane Forman and team are committed to building the region’s most trusted directory by verifying listings and connecting local businesses with loyal customers across Missouri and Illinois.