A used truck is not a machine purchase — it is a business you can drive, and it should be underwritten like one. In twenty-three years of fleet remarketing I have watched buyers agonise over paint and ignore the ECM report, haggle over $500 and miss a $9,000 frame problem. This guide is the order in which professionals evaluate a used commercial truck, and the traps that catch everyone else.
Start with the ECM, not the odometer
Every modern diesel truck stores its real history in the engine control module: total miles/kilometres, engine hours, idle percentage, fuel economy, hard-brake counts and fault history. An ECM download is to a truck what a service history is to a machine — the single most valuable document in the deal. A seller who refuses an ECM pull is answering your question. Compare ECM mileage to the dash odometer; a mismatch ends the conversation.
Mileage means nothing without duty cycle
A highway tractor at 700,000 km of steady line-haul can be a better buy than a 300,000 km tipper that spent its life overloaded on site roads. Ask what work the truck did — the ECM idle percentage and average speed tell you if the answer is honest.