My 2011 Yukon's 5.3 LC9 has 192,000 miles on it overall, mostly highway and some moderate towing a few times a year (lightweight camper), and the AFM has been disabled for 70,000 miles now. Naturally it has the blow-by and oil consumption problems. I do 3,000 mile oil changes and was going through a quart every 500 miles. The cylinders, plugs, valves, and injectors were carbonized. I finally got it to run better again, and put in new plugs and Seafoamed it a few times plus run lots of Marvel Mystery Oil in the gas and oil. It is running good. It has a bad cold start issue still, but is getting better. PO172 and PO175 (running rich) came a few times and the fuel trims were hella rich, but since using a different PCV set-up my fuel trims are getting back to normal and the codes haven't returned. Fuel mileage has been terrible, but started to improve when I made changes to the PCV system. My question is..... the line from the right valve cover (green in diagram) does which: bring air into the crank case, or blow air out? Mine blows out. The tech manual says it should suck in air. I also put on a vented oil cap per a TSB I found. The intake is much cleaner now and the carbon is slowly going away. Anyone else having problems like this? What was your solution? it seems fixed for now. I don't have inspections in my state so there is no emissions to worry about.

My guess for water in oil is the oil cap is sucking in air (it is wet and damp here this winter) and it isn't getting sucked out, so it just churns in the oil. Once I tried the 4th set-up the water issue seems to have gone away.

I avoid the GM dealers at all costs, but I did take it to them to ask about different remedies to fix the issue and of course their answer was literally, "Your engine is shot, time to trade in." I said I'm not trading in a P.O.S. for another P.O.S., and then the mechanic came in and said it would need a new engine to fix properly. It is running fine now, and I'll drive it until it locks up.

 

Dont know if you want to keep the vehicle. but a motor burning a quart of oil every 500 miles means that you really need an engine overhaul or new/used motor. I wouldn't drive a vehicle using that amount of oil. It all depends on what you want to spend or can afford. I've seen so many people with issues on the AFM that I wouldn't touch one at all. I'd put a non-AMF motor in your vehicle. Might need a new or used ECM for a non AFM motor as well.

 

My '11 5.3 Tahoe at 115k miles uses a qt. every 6500 to 7000 miles. AFM disabled since 35k when I got it. I changed the O2 sensors at 100k miles, plugs at 80k and with the fresh O2 sensors got back 2 mpg. . Always do plugs in my fleet at 80k and now will also do the front O2 sensors with the plugs. O2 sensor did not set any codes either when I changed them. I suspect they were just getting ''lazy''.
It gets tow duty with a pontoon and a 6x12 cargo trailer. Only full synth. fluids also.
Sucking down a qt every 500 miles and not leaking means those rings are toast and no amount of messing with the PCV system is gonna compensate for blow by on the rings as the blow by is the source of moisture in the oil.
There is water in gasoline, same as what drips out the exhaust pipe.