Is a clean Carfax enough before buying a diesel truck?

No. A clean Carfax is useful, but it is not enough. Vehicle history reports can show title events, reported accidents, mileage records, some service visits, and ownership history. They can also miss things. Private repairs, cash accident repairs, skipped maintenance, hard towing, tuning, emissions changes, rust, and poor repair work may not appear. Use the report as one tool. Then inspect the truck. Check the title, VIN, service records, cold start, leaks, rust, tires, brakes, suspension, transmission shifts, emissions warnings, and seller story. Ask what work was done before resale and what repairs were recommended but not completed. If the report and the truck disagree, trust the truck. A clean report does not make a rough diesel clean. A good inspection and real records matter more than a tidy history page.