I have a question for fellow BITOG experts. I'm curious about heavy engine load and it's affect on the oil and engine stress. My particular example is for my GM 5.3L Silverado (2012 which has the 6 speed and 3.42 rear gear) where I tow a 7500lb travel trailer. When I'm towing the trailer and come to a long and steady hill (let's say a long 6% grade as an example) I have two options. Going up the hill I can climb it at WOT and it will hold 3rd gear around 4k rpm. It won't accelerate but it will hold the speed at 45mph (It's not a race to the top and I can regularly pass Semi's). The second option is to downshift to 2nd gear which brings the rpms up to ~4.5k. Under this condition I can hold the 45mph with 50% throttle and can easily accelerate up the hill (with rpms rising accordingly). At 4.5k rpm the engine is really working but still well under redline. All of these numbers are estimates and what I remember off the top of my head. So, my question is this - which is easier on the engine and the oil? What is happening to the oil under these conditions? Is the oil better protecting the engine with less wear if I down shift and run at higher rpm (and thus need less throttle)? I usually downshift in this case but it got me wondering what is happening to the oil in this case. Your feedback and technical information is appreciated.