U.S. grain producers are facing higher operating costs as the ongoing conflict involving Iran pushes up diesel and fertilizer prices. Diesel reached $5.652 a gallon, up from $5.454 a week earlier and $3.713 a year earlier, while several fertilizer categories also recorded substantial increases. The latest reading differs from an earlier report that put U.S. diesel at $5.62 a gallon, near the 2022 record of $5.82, and from a separate mid-August 2026 reading of $5.454. Diesel is essential for farm machinery, trucks, trains and heavy equipment, allowing higher fuel costs to spread through freight, goods and services. Tight distillate supply, diesel crack spreads above $100 a barrel and geopolitical risk have supported refiners and oil-company margins while adding pressure to producers and consumers. Market pricing shows slight support for the probability of crude oil reaching a new all-time high by year-end. Investors will watch developments in the Middle East, OPEC and IEA responses, attacks on Russian refineries, and any changes in supply policy.