What should I look for in a diesel truck under $30,000?

Under $30,000, prioritize condition and documentation over the newest year or biggest trim package. Start with clean title history, maintenance records, rust condition, tire age, brake condition, suspension wear, leaks, cold-start behavior, transmission shifts, and whether the truck was used for heavy towing or commercial work. Be careful with listings that spend the whole description on wheels, lift kits, tunes, or cosmetics but say little about service history. Budget for immediate maintenance after purchase, especially fluids, filters, tires, brakes, batteries, and front-end work. The best buy is usually the truck with fewer surprises, not the one with the longest option list.