Inspecting a pre-warmed car
A cold start is a one-time diagnostic event per visit: startup rattles, smoke on first fire and cold-idle behaviour reveal wear that disappears within a minute of running. Sellers who warm the car before you arrive erase that evidence, deliberately or not. Ask for the car cold, and in summer add a hot-restart test after a ten-minute heat soak.
Trusting the registration test as a condition report
The Tasjeel or ADNOC test is a roadworthiness screen that takes minutes on rollers and gauges. It says nothing about paint depth, gearbox health, AC capacity, timing components or flood history. Treat a fresh pass as the floor requirement and the independent inspection as the actual assessment of what you are buying.
Reading a cleared fault memory as a clean car
An empty fault list with incomplete readiness monitors means the memory was wiped recently, which is the opposite of reassuring. Insist on a re-scan after 50-100 km of driving, or make the deal conditional on it. The absence of history is a finding, not a pass.