I am not brand loyal, but I do tend to continue to use specific products that have worked well for me. I use Mobil 1 in 0W/30 AFE and 5W/30 in my cars and trucks. I use 15W/50 Mobil 1 in one of my motorcycles, and I use Delo 5W40 or Rotella T6 interchangeably in the other.
I have found Redline gear lubes to be superior, especially in manual gearboxes. Redline products are all very good, but do not pass the cost/benefit test for me, except for things I need to shift.