We've run our TR98 in wheat and canola, and our old TR86 in Barley. No oats, but it does thresh wild oats out quite well. The 98 has 1600 hrs on the thresher right now and its in pieces for a rebuild in our shop.
Anyway, our oilpan gasket is seeping a little bit, but we just add oil. It maybe takes a liter a week, so its nothing to complain about. The engine, however, is amazing on fuel. We can run 12 hours on a 100 gallon tank of fuel and not be able to put 90 gallons in it the next morning when we fuel it up again.
Had ours at Swift Current 4 or 5 years back and they said that the snap rings will break in the driven rotor pulley and make a mess, so they cut the groove bigger and double snap ring it. No problems at all.
If you're needing concaves, I would recommend harvest services out of Craik. 5 years on them and we're flipping them side for side to wear the other way. They have been incredible and are very very strong.
The rotors wear rather quickly but they do a lot of work. We run durum and hard red spring wheat through the machine, probably the most abrasive crops around, so we'll get about 900 hrs until a total rebuild. Watch out for the rotor covers too, they wear through over the top because the clearances are too tight, the new CRs have addressed this.
The cleaning system is excellent. If there is one reason to stay away from a axial flow its the durability of the cleaning system. That gets expensive quick!
The bubble up gearbox seems to be a weak point for these machines. There have been a lot of upgrades to them over their lifespan. We have put 2 into our TR98. just replace the guts and you're good to go again. Not a hard job, just something to look out for.
As for capacity. It ran with a 7010 this year, and it has shown a 06 9660STS a few things about cutting fast and making a good sample. The amount of work per horsepower that you get done with a TR is unmatched. In the tough stuff they will rumble and grunt, but the worst is swaths that have been rained on. They kind of lump in all the time. if you can straight cut most everything, you'll be laughing. These are quite the straight cutting machines.
The cabs are crude compared to the CR/CX and 8010s, but they are very user friendly and you have everything you need right there. They aren't sealed up that great and they are a little cramped, but for being brought in with the 86 and 96s they are quite good still. If I were you I would buy the machine.