@alphaeighteen you might consider Mobil 1 10W-40 High Milage. It's got more seal conditioners. It stopped the light smoke I would get at startup due to old valve stem seals.
For the transmission inspection plate, I think they're talking about the black plastic cover on the back side of the...
That's not at all how oil works.
The first number tells you how it behaves at below-freezing temperatures. The second number tells you how thin it gets at high operating temperatures. So, a 5W-30 it gets no thicker than a 5 weight would below freezing, and no thinner than a 30 weight would at...