Yes, to answer the first question. Things wear out. And these trucks somehow run pretty darn good even when thing are really worn out.
Could very well be the rings. At 225,000, really, it could very well be time for a rebuild. If you just replace the specific thing causing the oil comsumption and put it back together, you'll
probably be back in there again before long fixing the next thing that wears out. You sure it's burning it and not leaking? Because a seal leak I would just fix, but if it's starting to burn a lot of oil, it's probably just getting old & tired and things are finally wearing out, and it may not stop at that one thing.
Just think how nice a rebuilt engine would be.
But hopefully some people with some more experience will chime in, too. I just know what happened to
my engine.