I haven't been paying attention to gas prices because I live so close to work and a tank seems to last me forever. I do work with dozens of small trucking companies and gas stations, and the price of diesel seems to have dropped below the $4 mark in most of the country, with the exception of a few places that are still selling for $4.01-4.03.
If if keeps up, it will be a huge relief. Those companies are spedinging $300-700 on each truck, every day. Some of them have more trucks than I can count, most are small operations with two, three, or half a dozen vehicles.