New to the forum and looking for advice . I have a 2011 Silverado 3500 with the Duramax with about 180,000 miles . My fuel consumption has increased recently for no apparent reason . It went from high 16 s down to mid 13 s . No trouble codes but I did have an issue with the secondary injector in the particulate filter some ago and it was replaced but the fuel consumption was fine after that until just recently . I suspect an emission issue somewhere . Anyone’s insight would sure help . Thanks, Larry .