A supply shock (a sudden disruption to available output from a key producer) tied to Iran has pushed US diesel prices to a record $6 a gallon. Diesel powers farm equipment and freight trucks, and it runs the industrial machinery that manufacturing depends on, so a record pump price is also a record upstream cost for food and goods before they reach a store shelf.
The squeeze arrives as Americans are already navigating a broad affordability crunch. Most households never fill a diesel tank themselves. They absorb the higher cost indirectly: through grocery prices and through delivery charges on goods that shipped by diesel truck.
Agriculture and industry are the two sectors most directly exposed. Farmers planting and harvesting crops have no quick substitute for diesel. Factories and distribution networks moving heavy loads face the same bind. When the fuel that underpins both sectors hits a record, the pressure on consumer prices spreads wide.
The Iran supply shock is what drove the record. When output or exports from a significant oil producer face sudden disruption, global crude supply tightens faster than buyers can adjust, and terminal prices climb to the pump.
At $6 a gallon, US diesel has reached a level it has not seen before.