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lou’s garage

My 2009 Chevy Silverado 5.3-litre burns oil at an alarming rate and my dealer is recommending an out-of-pocket engine replacement due to an AFM failure. Any advice would be appreciated. – Jesse

The Active Fuel Management (AFM) system used on this engine is designed to turn your V-8 truck into a fuel efficient V-4 by shutting down four cylinders while at cruising speeds. However, when the four cylinders shut down, this is when the oil consumption problems start. GM says there are two potential problems. First, excessive oil from the deactivated cylinders gets pushed into the PCV system and eventually into the intake manifold where it gets burnt. Secondly, the AFM pressure relief valve in the oil pan may deposit too much oil on the cylinder walls for the piston oil rings to handle, causing the rings to eventually seize up.

GM has several repair bulletins, including one where the valve cover is replaced with a new redesigned piece that guides the oil away from the PCV port and a updated AFM pressure relief valve shield. For those vehicles that this repair does affect, a suitable fix GM has several other escalating repairs – starting with engine decarbonization, engine disassembly with ring replacement, all the way to complete engine replacement.

I assume that since the dealer is recommending engine replacement that the updates have offered little symptom relief. If you have proper maintenance records and documented complaints of oil consumption while the vehicle was still under warranty, call GM Canada and ask for some form of assistance.

Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail globedrive@globeandmail.com, placing "Lou's Garage" in the subject area.

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