California’s record diesel prices are hammering trucking companies already squeezed by soaring insurance, equipment and regulatory costs, with some warning they can no longer afford to keep their rigs on the road. The statewide average hit a record $8.39 a gallon Friday, according to AAA, up from $7.98 just one week ago and $5.17 a year ago. In Los Angeles and Long Beach, diesel averaged $8.36 Friday.