Diesel prices are edging down closer to the $3.50-a-gallon mark, with national on-highway diesel selling for $3.656 on average, the U.S. Energy Department’s Energy Information Administration (EIA) reported Monday. That’s the lowest it’s been since July 2, 2012, and a whopping 4.2 cents less than the $3.698 a gallon it was selling for last week. Diesel prices have been dropping every week since June 30 except for the weeks of Sept. 1 and Sept. 8, when it stayed the same. Diesel is 23 cents below what it was at this time last year.