Diesel down slightly after nearly two months of increases by admin | Aug 22, 2017 The average price of a gallon of on-highway diesel went down two-tenths of a cent to $2.596 per gallon for the week ending Monday, Aug. 21. This marks the first decrease after seven consecutive weeks of increases. Powered by WPeMatico Share this:Tweet Related Submit a Comment Cancel reply Your email address will not be published. Required fields are marked *Comment Name * Email * Website Notify me of follow-up comments by email. Notify me of new posts by email.