Oil Fouling/consumption Question

[Ghost-Flame]

Hey I have made comments about this before. I'm becoming more concerned.

2002 e53, 3.0, 133,000 miles

Here are the symptoms:
-oil fouled plugs
-hard starting when warm,
-quick/first time start when cold
-oil spots on trailer after 3,000 mile trip
-uses 1 qt every 1500 miles

I alternate between M1 0-40 or castrol syntec 5-30. It doesn't seem to matter which oil.
Would a thicker oil be better? I experience 5 degree weather here sometimes in the winter. Do you have any suggestions about an oil choice or repair or do nothing?

Otherwise the car runs great, no noise/very quiet, feels like a new car power and engine wise. Lots of power pulling trailer etc.