From the things I've read it seems that the CP4.2 will last as long as the entire fuel system has been designed and maintained properly. It's needs good filtering and delivery and I think that's where a lot of manufactures fell short right after the 2007 changes. Most diesel fuels today are using some % of bio mixture that will give you the protection that's needed without additives. Can you give a link or test results of fuel tests from various locations? I live on the east coast in a highly traveled area so the fuel doesn't sit for long periods of time.