First of all bigoilburner, yes turbos can definitely be rebuilt. Usually if they aren't too bad that means bearings and seals and 1-2 hrs of your or a shop's labor. If there'sa lot of abrasive damage then a new compressor wheel is needed and if forbidden guests have been getting to know each other (IE compressor wheel hitting housing etc) more extensive repair may be required. @93 1 quart per 300 miles really isn't terrible on a 6.9 with a few hundred thousand miles on it. A 6.9 usually burned some oil even when they were newer. An exception could be a really tight rebuild or an engine that was broken in properly(IE not babied too much so the rings didn't have to work against an oil glaze built up on the cylinder walls) a 6.9 also had non positive valve stem seals. @Black Dawg, I might also suspect the turbo seals in your case, usually it's the rings, but if blowby and smoke seem the same and your turbo is a bit loose, well you might even want to pull that thing off and thrw a turbo kit at it. Probably consideringa ll the wrenching and custom work you've done on IDIs a turbo overhaul is withing your level of expertise provided it only needs the bearings and seals. It would probably be pretty cheap compared to any other option you might have other than doing nothing and let it develop, which also might not be cheap in the long run.
