As a pre purchase samples are valuable to tell if there is coolant in the transmission or engine oil in the coolant, that sort of thing. Wear metals may or may not show, depending on the last fluid change. The state of the coolant is also important, that is, are the corrosion and pitting resistance up to standards. The generator, not so much, as the engine is not as costly as the transmission or the main engine.
Jim and Jennie, Cats=Bittles and Potter, 2000 Dynasty 350 ISC
2013 Silverado 4x4 Towed with R1200GS in bed.
PROV23:4 Do not wear yourself out to get rich; have the wisdom to show restraint.