Hit 5,000 hours on my Cummins rebuild log, still surprised

Started keeping a rebuild log back in 2021 when I did my first full tear down on a 5.9 in my shop outside Denver. Never planned to track every oil change, injector swap, or torque spec, but I got bored one night and just started writing it down. Checked the other day and hit 5,000 logged hours, which blew my mind because I thought I'd maybe have 2,000. That number matters because it means I've actually seen patterns in failures, like how certain seals go at around 1,200 hours if you don't warm up proper. It's also caught me twice where I thought a knock was new but my notes showed it showed up at 800 hours in a different rig. Anyone else keep a detailed log like this or do you trust your memory on maintenance intervals?

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the_wren23d ago

Logged hours and running hours are not the same thing, and that's a big part of the story. 5,000 logged hours just means you've spent that much time writing things down, not that the engine has seen 5,000 hours of work. You'd have to add up all the time stamps on your actual maintenance sessions to get a real engine-hour count. That seal pattern you noticed might be based on 2,000 actual running hours, not 5,000, if you're counting bench time and note-taking. Still, the log itself is the key part, because it catches those repeats like the knock showing up in a different rig. Memory is garbage for this stuff, I've watched guys swear a part is fresh only to find out it's got 3,000 hours on it.