2012 Terrain 3.0L V6 flex fuel engine with 207k miles Oil was in one of the spark plug tubes (middle front cylinder - didn't look up the #). Not much oil but noticeable. Next step it would naturally seem (intake manifold already off) is to replace the valve cover gaskets & spark plug tube seals. What is the valve cover bolt torque spec? Also, I found the below when reading up some on this problem. Anyone have the bulletin where this was issued? My first step is to rule out the valve cover gasket & spark plug tube seals, but this is looming. Vehicle sets a general misfire code every week or so but no driveability issues yet. Fluid in Spark Plug Tubes March 25, 2013 A Check Engine light may be illuminated with misfire DTCs set, or a possible oil or coolant leak may be found, on some 2010-2013 Enclave, LaCrosse, CTS, SRX, Camaro, Equinox, Traverse, Acadia, Terrain; 2012-2013 Caprice PPV, Captiva, Impala; 2013 ATS and XTS models equipped with 3.0L and 3.6L (RPOs LF1, LFW, LLT, LFX) HFV6 engines. (Fig. 10) On inspection, coolant or oil may be found in a spark plug tube. Determine if the oil or coolant is coming from the spark plug tube and not leaking into it from above. If the spark plug tube is leaking, replace the cylinder head, spark plug and coil. Porous spots in the head created during manufacturing cause the leak. The spark plug tubes are permanently sealed into the head and are not replaceable. If a cylinder head is replaced for this condition, mark the faulty spark plug tube before sending the head in for warranty or core so GM Engineering or the re-manufacturing facility can identify it.