What should a mechanic do for a high mileage tuneup?

For a high mileage tune-up, a mechanic should first inspect and replace worn spark plugs, which can affect engine performance. They should also check and replace air and fuel filters to ensure optimal airflow and fuel delivery. Additionally, the mechanic should examine the engine oil and consider changing it along with the oil filter, and inspect the ignition system and other vital components like belts and hoses for wear. Finally, a thorough diagnostic check can help identify any other potential issues that may need addressing.