Ash Loading
WARNING: This page is about a different car, the 2012 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
Ash is a non-combustible by product from normal oil consumption. Low Ash content engine oil (CJ-4 API) is required for vehicles with the exhaust particulate filter (EPF) system. Ash accumulation in the EPF will eventually cause a restriction in particulate filter. Regeneration will not burn off the ash, only particulate matter is burned off. An ash loaded EPF will need to be removed from the vehicle and cleaned or replaced.
Muffler