The quickest and most affordable response to historically high diesel prices is also the simplest: Use less of it.

Why it matters: Diesel is so entrenched in farming, trucking and other industries that even soaring prices aren't enough — at least not yet — to prompt a wholesale shift to alternatives from electric semi trucks to manure-powered tractors.

Catch up fast: Diesel prices have climbed to record highs since the U.S. war with Iran began in March, rising faster than gasoline amid global oil supply disruptions .

Diesel averaged $6.31 a gallon Thursday, up 74% from a year ago, according to AAA . Regular gasoline averaged $4.27, up 39%.

The big picture: Gasoline gets the attention, but diesel is the workhorse of the American economy.…