I installed a Dieselsite.com coolant filter on my 2003 Excursion Ltd 4X4 with 6.0L motor back on June 5, 2005 (51,090 miles) and just changed it today, September 18, 2005 (57,150 miles)... 6,060 miles since installation of coolant filter.
First off, let me say that I installed a coolant...