2015 Chevrolet Silverado Update to Improve MPGs By Luke Vandezande May 09 2014 Share this Article Tweet General Motors is planning a handful of tweaks and updates for its full-size trucks that will take effect in the 2015 model year. Continue Reading... Filed under: American GM TrucksTags: 2015 sierra, 2015 silverado, automatic, Chevrolet, eight speed transmission, fuel economy, GM, GMC, mileage, mpgs, pickup trucks, Trucks