We use two steps: 1. Insert a medical-grade endoscope through the spark plug hole to visually inspect cylinder wall scratches and carbon buildup on the piston top; 2. Extract an engine oil sample to check for large metal debris or emulsification (caused by coolant leakage).

As rubber seals age, "slight oil seepage (oil stains but no dripping)" is very common in used cars and is not considered a major fault. Our recommendation is: as long as the oil level does not drop abnormally, just clean and monitor it regularly after arrival, without the need to immediately incur high costs to disassemble and replace the seals.

If insurance claims records are accessed, there will usually be notes like "the insured vehicle is fully responsible for hitting a fixed object" or "third-party liability insurance payment." We can roughly reconstruct the accident scene based on this and cross-verify the stress points on the vehicle's frame with paint thickness gauge data.