During summer months my coolant temps register 180F unfailingly, except for several mile and greater distances with long 6% grades. Got my diesel reassembled and took a short Interstate run at 70mph. Max temp at 20F ambient temp is 170F. This is fine with me as long as combustion of the fuel is as complete as it is at 180F. Could you folk's advise me as to whether I should partially shield radiator with cardboard, or like material, to bring Interstate temps back to 180F for winter months?