The Ford F-150's five-decade reign as America's best-selling truck has included some stellar engines and some notorious duds. While models like the 300-cubic-inch Inline Six and 3.5L EcoBoost V6 have earned praise, certain engines have become infamous for reliability problems and expensive repairs. These problematic units have cost owners thousands in maintenance and replacement costs.

Leading the list of engines to avoid is the 5.4L Triton V8, which mechanics have dubbed 'absolute trash' due to recurring spark plug failures, oil sludge buildup, and timing system issues. Early 3.5L EcoBoost V6 engines also make the list, suffering from timing chain problems and cam phaser failures that prompted multiple technical service bulletins. The 4.2L Essex V6 rounds out the problematic trio, known for intake manifold gasket failures that can cause hydrolocking and bent connecting rods.

The 3.0L Powerstroke V6 diesel and 6.2L Boss V8 complete the list of engines to steer clear of. The diesel struggled with crankshaft bearing failures and EGR system problems, while the high-performance Boss V8, though durable when maintained, can develop costly issues like broken valve springs and spark plug failures in neglected Raptors.