Fellow 2.0 ABA guy here.
Unfortunately not tarbo though
I ran Valvoline SynPower 5w-30 for a while, and had the same problems as you though. Do you get a lot of blowby through your PCV? If you do, I'd recommend switching to a heavier weight oil, 10 or 15w-40, for the summer.
When you run open PCV, you can definitely tell if your oil is thinning too much. lol. I've used Rotella 15w-40 for my last two oil changes, and am totally satisfied. No more problems at all with the oil buzzer or oil thinning.
Of course, it could also be something worse, like a oil pressure sensor, failing oil pump, etc...I'm sure someone with more knowledge of these things will chime in.





