Full explanation
Engine hours run from engine start to stop regardless of whether threshing occurs (field transit, idle, maintenance). Separator hours count only when the threshing drum is active (grain passing through sieves and straw walker). The gap matters: a typical Ukrainian grain-combine season is 800 engine hours = 600 separator hours (ratio 0.75). Why it matters when buying used: (1) high engine hours with low sep/eng ratio (<0.5) means the combine spent much time idling — sieves and rotor worn less than headline figures suggest; (2) high ratio (>0.9) — intensive threshing use, so all threshing components are heavily worn; (3) 0.7–0.85 indicates normal duty. For John Deere S-series, Case IH Axial Flow, CLAAS Lexion — rebuild of a sieve-and-threshing kit after 3,000 separator hours costs USD 2,500–5,000.