Failure mode - GM 6.0L V8 Gasoline (GM HD, LY6-L96 2008-2019; Express/Savana vans 2008-2020)

Oil consumption at high mileage (Gen IV theme)

Reliability tier: aggregated - verify before ordering, see /disclosure/

Symptoms

oil level dropping between changes without visible leaks; fouled plugs on high-mileage engines

Compare with the other causes of the same sign on this engine: oil leak, oil consumption or rising oil level

Root cause

Ring and valve-guide wear at high mileage lets oil into the chambers without an external leak; the HD 6.0's iron-block short block is durable but not immune at six-figure odometers. PCV system faults exaggerate consumption readings.

Diagnosis

rule out external leaks first; measure consumption over a fixed interval
compression/leak-down to separate ring/seal wear from valve-guide wear

Fixes

service as diagnosis dictates (PCV check, plug renewal, filter service at the interval; top-end work at extreme mileage) ()

spark-plug - more than one option: GM 6.0L HD Spark Plug 2008-2014 (OEM), GM 6.0L HD Spark Plug 2015-2019 (OEM)
GM 6.0L HD Oil Filter Assembly (OEM)

Prevalence

occasional