Farm diesel in Illinois set a record of $5.63 per gallon and would push fuel and oil costs to $28 per acre for corn and $24 for soybeans, $6 and $5 more than in 2025.
The average price of diesel for agricultural use in Illinois reached a record $5.63 per gallon in the Agricultural Marketing Service (AMS) report of Oct. 16, the highest level since the series began publication in September 2008. That increase would raise fuel and oil costs to about $28 per acre for corn and $24 per acre for soybeans on central Illinois grain farms with high land productivity, $6 and $5 per acre more than in 2025, respectively, according to authors Gary Schnitkey, Nick Paulson, Jim Baltz, Carl Zulauf and Bradley Zwilling.
The escalation intensified in late February and early March 2026. On Feb. 20 diesel averaged $3.14 per gallon in Illinois; in the following report, dated March 6, it rose to $3.90, an increase of $0.76 that coincided with the start of the conflict with Iran on Feb. 28. From there it kept climbing to $5.41 on May 1, then fell to a low of $3.79 on June 26 and climbed again to the current record levels.
If current levels hold through the rest of the year, the Illinois annual average will be $4.30 per gallon in 2026, 50% above the $2.84 average recorded between 2009 and 2025. The previous annual high was $4.29, set in 2021.
Between 2009 and 2025, fuel and oil costs for central Illinois grain producers averaged $19 per acre for corn and $17 per acre for soybeans. With a projected annual price of $4.30 per gallon, those costs would come in at approximately $28 per acre for corn and $24 for soybeans.
The projected cost of $28 for corn would be $9 above the 2009-2025 average of $19 and $6 higher than the $22 of 2025. For soybeans, the projected $24 would be $7 more than the $17 average and $5 more than the $19 of 2025.
Despite the increase, fuel accounts for a relatively small share of total production costs: between 2019 and 2025 it equaled 2.8% of non-land costs in corn and 4.2% in soybeans. The authors caution, however, that more expensive diesel can also raise transportation and distribution costs for farm inputs, indirect effects that they do not estimate in this analysis.
Illinois' projected 2026 budgets already include fuel and oil costs of $28 per acre for corn and $23 per acre for soybeans. For 2027 further increases are projected, to $30 per acre for corn and $26 for soybeans.
Machinery costs are updated every two years; the most recent estimates, from 2025, used a diesel price of $3 per gallon. With the increase in fuel costs, the authors calculate surcharges for custom operations using the formula: (current diesel price minus baseline price) multiplied by gallons used per acre, rounded to the nearest multiple of $0.10.
For the calculation a current price of $5.60 per gallon is used, close to the most recent costs in Illinois, and the surcharges apply to fall operations. In the case of the chisel plow, whose estimated 2025 cost was $19.50 per acre with use of 0.7 gallons per acre, the additional fuel cost comes to $1.82 [(5.60 − 3.00) × 0.7], rounded to a surcharge of $1.80, bringing the new total cost to $21.30 per acre.
For tillage operations, surcharges range from $1.60 per acre for field cultivation up to $5.70 for a coulter chisel plow. At harvest, the combine cost for corn is estimated at $54.40 per acre, with use of 1.07 gallons per acre, which yields a surcharge of $2.80 per acre at a price of $5.60.
For soybeans, the combine cost is estimated at $47.60 per acre, with 0.70 gallons per acre, and the surcharge comes to $1.80 per acre.
In short, higher diesel prices would raise 2026 fuel and oil costs by $6 per acre for corn and $5 for soybeans versus 2025. Those costs remain a minor fraction of non-land costs, Illinois' current budgets already reflect most of the increases, and the surcharge formula makes it possible to adjust custom machinery costs to changes in diesel prices.
