Mobil one , 5w30. I did add motor medic valve medic oil detergent
Could the additive have thinned out the oil?
I've recently revisited my oil chart, comparing this oil against that oil on a spreadsheet. I too am running plain old M1 in mine.
Shell Rotella Gas Truck, Quaker State Ultimate Durability, Redline and even the latest ACDelco Dexos 1 Gen 2 oil is thicker than M1, has a higher viscosity number and around the same viscosity index number.
M1 is not the same as it was even nine or ten years ago when I started using it thirty some years ago. It's no longer a Group IV base oil formula.
So I think next time around it's going to be ACDelco; they even have a specific oil for the aluminum engine recommended on their website. I found it cheap over at GMPartsGiant too.
FYI:
10-9234/88865905 - 1 Quart Bottle
10-9147/88865743 - 5 Quart Bottle
10-9165/88865763 - 6 Gallon Box
Well, after all that rambling on, I guess my point is that you should maybe try a thicker oil. Same 5W-30 just slicker and thicker! The choice of filter is pretty important too for flow. Some just don't flow worth a plate of beans.