This is the 2015–present GLC generation (W253) in diesel/automatic form, commonly seen as 220d/250d-type engines paired with Mercedes' 9G‑Tronic auto box. Diesel models have DPF and (on Euro6 variants) AdBlue/NOx equipment, so they prefer regular long runs rather than constant short trips; some cars also came with optional AIRMATIC air suspension, which is comfortable but can be costly to repair if it fails. Dealers sometimes tag the GLC Coupe separately — confirm whether this listing is the regular SUV or the sloping-roof Coupe, as the Coupe sacrifices rear headroom and boot space.

• 9G‑Tronic transmission behaviour and service: feel for smooth shifts, no hunting or hard shifts, and ask for evidence the gearbox oil/filter was serviced per Mercedes intervals.
• DPF and EGR condition: check for frequent regeneration events, heavy smoke/soot, and black deposits in the intake or oil which indicate excessive soot contamination.
• AdBlue system operation: verify filler access, that the dosing system has no warning lights, and that the tank and pump are intact (some Euro6 diesels require this).
• AIRMATIC/air suspension (if fitted): check for sagging, compressor noise or long pump-up times and listen for leaks when suspension cycles.
• Turbo and oil leaks: check for boost lag, whistling/odd noises, and oil seepage around the turbo/intercooler pipes and valve cover seals.