Hey subi400. We bought the car at 40k used. It had oxidized oil inside of it, a decent coating. I moved it to mobil 1 because it was cheap at costco. I assume the previous owner used some dino oil that was prone to leaving that nice brown layer of oxidized burnt oil on the internals.
Mobil 1 5w30 does seem to turn into water in this car, the same all mobil 1 oils seemed to do in my 3076R 1.8T Jetta.
I had no issues in my Jetta with total 5w40, I was going to give that a try next oil change to see how the EJ253 likes it. I did some searching (GASP SEARCHING WITH A LOW POST COUNT!!! OMG) and it seems you guys prefer the rotella.
The plug wire thing, I actually ripped it myself removing it and then reinstalled it to see what would happen. I thought it was funny I had no misfires but the car would obviously lose spark sometimes and other times have weak combustion events(you could feel it especially near idle), but nothing in the ECU.
I've done marvel mystery oil mixes in super high mileage cars, about 1/2qt and under 3000rpm driving. It does well melting the gunk out, but it does thin the oil some. I usually add 1qt right before an oil change and put around below 3k in this 07 2.5i, it seems to pull the garbage out fast as the oil gets dark quick.