Exhaust gas
Exhaust gas temperature margin erodes with usage, one or two performance restoration shop visits, costing $0.3-$0.6m for a -5 series, can be performed before taking the engine off wing, which can restore 60% to 80% of the original margin; after that, the life limited parts must be replaced, after 20,000 cycles for the hot section ($0.5m), 25,000 for the axial compressor and 30,000 for the fan and booster ($0.5m-$0.7m) for a recent CFM56 : the whole engine parts cost more than $3m, $3.5 to $4m with the shop work-hours, around $150 per cycle.