Excessive oil consumption on some 2010-2013 LaCrosse, Equinox, Terrain and 2011-2013 Regal models equipped with the 2.4L engine (RPOs LAF, LEA) does not require engine replacement. If excessive oil consumption is confirmed after an oil consumption test, new pistons and piston rings should be installed.
Piston Ring Coating
The top compression ring in the new kit has a more robust coating on it that is designed not to wear as quickly as the original coating. Tests indicate that it wears about 4-5 times longer than the original coating.
If the top compression ring is worn, it will allow combustion pressure past it, which causes the oil control rings to be less effective and results in excessive oil consumption.
On 2010-2011 vehicles built before March 2011, there is a strong correlation between leaking high pressure fuel pumps diluting the oil and causing the ring wear. Due to this, check the fuel pump, balance chain, balance chain tensioner and timing chain for the proper part numbers. The updated fuel pump has an enhanced seal.
If these updated parts have not been installed during a previous repair, they should be replaced when the pistons and rings are replaced. Use field action #12313 if the balance chain and/or fuel pump is replaced.
The pistons must be replaced because as the rings wear down, it starts to widen the piston ring groves. The worn grooves will not retain the new rings correctly.
The “zebra” stripping on the bore surface (Fig. 1) is not an indication of a cylinder bore abnormality, but rather a transfer of the ring material as it was worn down. The bores are still uniform and the new rings seal. The validation of the new ring pack was done on used blocks that had zebra striping. It’s not necessary to do any surface treatment to the zebra striped bores when installing the new pistons and rings.
TIP: Use only plastic scrappers to clean the sealing surfaces of the engine. Cleaning wheels and pads will leave material in the engine. An indication that cleaning wheels/pads were used will be an engine that runs for 2,000–4,000 miles after the piston/ring replacement and then develops an oil pressure condition or rod/main bearing knock for a worn bearing.
Refer to Bulletin #13-06-01-003B for additional information, including several other parts — such as balance chain guides and timing chain guides — that should be inspected for excessive wear as well as normal wear markings of other components, such as markings on the camshafts (Fig. 2) and roller follower.
– Thanks to Ron Caponey