Michigan's average gas price climbed to $4.89 a gallon Friday, Sept. 18, as drivers across Metro Detroit continued to face rapidly rising fuel costs.

AAA reported a statewide average of $4.8933 for regular unleaded Friday, up about 14 cents from $4.7551 Thursday and nearly 58 cents from a week earlier. Metro Detroit averaged $4.8375 a gallon Friday.

Earlier AAA data reported by FOX 2 Detroit showed Oakland County prices running above the statewide average on Sept. 16, while Wayne, Macomb and St. Clair counties had some of the lowest averages in Metro Detroit. That comparison should be treated as a snapshot because prices have continued changing quickly.

Some stations have already crossed $5. A Shell station on Dequindre in Madison Heights was charging $5.04 for regular credit on Thursday morning, FOX 2 reported.

Diesel reached a record statewide average of $6.6767 per gallon Friday, according to AAA, surpassing Thursday's $6.5405 average.

Oakland University Professor Michael Greiner told WXYZ that higher diesel costs ripple through the supply chain, raising prices on food and manufactured goods for everyone.

The surge is squeezing delivery businesses. Jason Lett, who manages Zoom 2Day Deliveries, a courier service, told WXYZ that overnight price spikes eat directly into the company's bottom line. He said the company is weighing whether to raise prices or wait for relief. WXYZ did not identify the courier service as being based in Farmington or Farmington Hills.

Gig workers face the same math. DoorDash does not adjust driver payouts when gas prices spike, meaning every cent increase comes out of drivers' pockets, WXYZ reported. Shanice Johnican, a DoorDash driver, told the station she stopped at a pump charging $5 a gallon after completing a $10 delivery order. "That's half my order for one gallon of gas," she said.

AAA said crude oil remained around $100 a barrel Sept. 17 as instability in the Strait of Hormuz continued to put pressure on fuel prices. FOX 2 and Michigan Farm News also reported that the U.S.-Iran conflict, attacks on Russian refineries and other global supply disruptions were contributing to volatility.

Michigan Farm News reported that Russia extended its diesel export ban through Oct. 31 and that U.S. diesel inventories had fallen to about 25 days of supply.

GasBuddy petroleum analyst Patrick De Haan warned Thursday that the spike was not over, saying diesel prices showed "no signs of slowing." Auto industry analyst Paul Eisenstein told CBS Detroit there seems to be "very, very little likelihood" of significant price decreases before 2027.

Michigan's motor-fuel tax is 52.4 cents per gallon in 2026, according to the Michigan Department of Treasury. The state eliminated the previous 6% sales tax on fuel when the new rate took effect Jan. 1. Treasury says 98% of motor-fuel tax revenue goes to the Michigan Transportation Fund for roads and public transportation.

Michigan's all-time record for regular unleaded is $5.22, set in June 2022. Friday's $4.89 statewide average was about 33 cents below that record.