I just purchased a used 09 Chevy Tahoe Hybrid with the 6.0 AFM engine. Was a quart low of oil after approx 1200 miles of driving. I could not determine if the previous owners had changed the drivers side valve cover or not without pulling it off so I went ahead and swapped it out. After I removed it I saw that it had in fact been replaced at some point so I did not gain anything except for I guess the satisfaction of knowing. It was a bit disappointing to see the interior condition of the existing valve cover, it is sludged up pretty badly. I think people following GM's OLM system cause a lot of high mileage sludge issues due to delayed oil changes. Any motor oil (including synthetic) will sludge if left in for too long. For you guys that are running the OLM down to 0% before an oil change take a look at this pic (below) of the interior of the valve cover, now keeping in mind that this is a 198k miles engine and will have some buildup thsi looks excessive to me..... The previous owner assured me that it had always had 5W30 synthetic oil run in it and was religiously changed per owners manual. Anyway I have driven for another 500 miles or so after the valve cover swap and the oil level seems to have dropped a little bit but not enough to ad any oil yet. Oil pressure is good with no odd engine noises or lifter clicks so hopefully it will run a long time. It has averaged over 17 mpg over the last 1700 miles or so, pretty good for a Tahoe with a 3.5" lift / 10x20 Mayhem 8106 Hatchets and a set of aggressive tread Nitto Grapplers. I am looking at changing out the front and rear differential and transfer case fluids soon. I will be curious to see what the fluids that come out will look like. Not sure how many Hybrid owners visit here? my intial search turned up no threads on hybrids................might be a lone wolf LOL
that had a lot of issues.
