Cook County drivers are paying close to $4.85 per gallon for regular gas, and the culprit sits about 50 miles south on I-55.
The Chicago metro average for regular unleaded reached $4.83 on Oct. 22, according to AAA. The national average stood at $4.27. Illinois diesel averaged $6.56 per gallon, down from a record $6.83 on Sept. 23 but still nearly 80% higher than a year ago. Cook County's retail average ran even higher than the statewide figure, hitting $4.85 per gallon earlier in October, AAA data showed.
Three overlapping refinery disruptions across the Great Lakes region are behind the spike, according to RE Journals.
The ExxonMobil refinery in Joliet, a 275,000-barrel-per-day plant in Will County that produces roughly 11 million gallons of gasoline and diesel daily, suffered a total power outage on Sept. 13 that forced an emergency shutdown. Flames and black smoke from the plant's flare system were visible on site, according to industry publication ChemNet. That single facility accounts for about 6% of all Midwest refining capacity. Its fuel feeds pipelines serving Illinois, Indiana, Iowa, Michigan and Wisconsin.
ExxonMobil had not finished recovering when a new problem hit. On Oct. 20, the company shut a 50,000-barrel-per-day catalytic reformer at the same Joliet plant after Wood Mackenzie observed decreased stack activity and elevated flaring, Texas Energy Report reported. An ExxonMobil spokesperson said Oct. 21 the company was working to resolve an operational issue but provided no restart timeline.
The Joliet outages coincided with planned maintenance at the Cenovus refinery in Lima, Ohio, which took another 185,000 barrels per day offline starting in September, according to RE Journals. The BP Whiting refinery in Indiana, the Midwest's largest, has also been running with restricted capacity. About 800 BP workers have been locked out since March 19 in a contract dispute with the United Steelworkers, In These Times reported.
What it costs here
The Bureau of Labor Statistics reported that gasoline prices in the Chicago-Naperville-Elgin area rose 6.3% from August to September. Year over year, the gasoline index climbed 28.9%. The BLS metro area includes Cook County.
The pain extends beyond the pump. Across northern Illinois, school districts that run their own diesel bus fleets are absorbing the hit. Kankakee School District 111 said its September diesel refill cost nearly double what it paid in September 2025, jumping from $3.75 to $6.76 per gallon, Shaw Local reported. Lyle Neal, the district's assistant superintendent of business services, told Shaw Local the trend could burn through a full year's fuel budget in seven months.
Naperville Unit District 203, which runs more than 120 diesel buses for roughly 16,000 students, expects to spend an extra $300,000 on fuel this school year if diesel prices hold, the Chicago Tribune reported. The district had already trimmed 900 miles per day from bus routes in the spring.
Whether Park Ridge-Niles District 64 or Maine Township High School District 207 face similar budget pressure is not yet clear. Both districts operate in Cook County, where fuel prices have run above the statewide average.
Relief uncertain
Patrick De Haan, head of petroleum analysis at GasBuddy, told the Tribune that diesel prices may decline slightly as the Joliet plant resumes operations. Per-gallon diesel had already dropped more than 25 cents since the Sept. 23 peak.
Longer-term, De Haan said the outlook depends on geopolitical developments. "A lot of that is a function of the continued evolution in the situation between the U.S. and Ukraine, and the U.S. and Iran," De Haan told the Tribune. "If we see some improvement in tensions there, then we could see some relief."
RE Journals noted that much of the current pressure stems from a temporary regional bottleneck and that prices should stabilize as the Joliet refinery returns and BP Whiting's maintenance ends. The Oct. 20 catalytic reformer shutdown complicates that forecast. ExxonMobil has not disclosed a restart date for the unit.
