Symptoms

Blue or gray smoke (burning oil)

What causes it depends on the engine. 4 documented failures on 3 engines list this among their signs. Pick your engine for the causes ranked, how to tell them apart and the usual fix.

7.3 Power Stroke (1994.5-2003) 1 known cause: Injector o-ring failure 6.4 Power Stroke (2008-2010) 2 known causes, most widespread: Piston ring failure #7/#8 (regen fuel wash) 6.7 Power Stroke (2011-present) 1 known cause: VGT turbocharger failure - generation dependent (ceramic-bearing GT32 vs journal-bearing GT37+)

Built from the failure-mode records on this site: a failure is listed when its own symptom list describes this sign. Engines not shown have no documented failure with it in our records. How we tier and source facts.