Original owner 03 GMC 1500HD 6.0 liter. 4x4 4.10 gears, original everything except normal maint items. at 160k started having flashing check engine light when cresting the top of a hill on the interstate, noticed when rpms were right around 2500 rpm. Scanned random misfire detected, took to gm shop, when I went back to pick up they already had trade value figured out for me or $2k to tear down and inspect camshaft, tech told me that this engine has a roller cam and they wear out lopes before flat tappet. YEH. OK the next morning I took off for a 2k mile trip with my tailer, now at 195k Ive towed my drag car to the strip almost ever weekend with this truck, it is not missing, it is DETECTING a misfire, mileage may have slipped a little over the years , but I didnt buy it for its mileage performance. THis truck has had many electrical gremlins, Reduce engine power on start up 3 times in 10 years. Most recent last week, shut it off started it 2-3 times and gone, check engine light went off after a dozen or so succeful starts, Also from time to time if you open gloove ox or turn on interior light the inst cluster will blink bed light indicator. 2-3 times Have had passenger side electrical windows(front and back) stop working, but next day all works ok. ALso have got in truck started truck jumped in and took off with door chime still going, stop turn off truck restart sometimes maye 3- 4 times before going off. always thought maybe starting before shutting the door, causes this one.