For gasoline cars, insist on a compression test: each cylinder should read within 10-15% of the others, and the actual values should match factory specs for that engine. A single low cylinder points to worn rings or valve problems that idle checks will never reveal. A leak-down test goes further. It pressurizes each cylinder and measures how much air escapes and where. Air hissing from the oil filler cap means ring wear; from the intake or exhaust means valve issues; bubbles in the radiator coolant mean a head gasket problem. This is the single most revealing test for engine condition. Also request OBD scan data with freeze-frame records, a coolant system pressure test (to catch hidden leaks), and an inspection of the timing belt or chain condition with service history. For electric vehicles, compression tests don't apply — instead ask for a battery health report from the BMS, motor insulation readings, and a road test logging any inverter or drive-unit fault codes. A written report with photos or video of each test is essential evidence for your records.

We will remove the chassis guard to physically inspect the battery pack's lower shell for serious dents or scratches, and check for signs of mud or sand intrusion in the waterproof vent at the edge of the battery pack.

Most models adjust through the central control screen menu, while a few models (like some BYD or MG) retain physical levers or paddles on the center console or steering wheel. We will check if the drag feel when the system engages is linearly normal.