I have a 2017 Duramax L5P with a Banks Derringer that I run on level 6 all the time. I tow a 15k fifth wheel and sometimes have another trailer behind it depending on what I am wanting to do. My 17 has a smaller oil cooler than the OP 2020 and Gale Banks did a comparison of the two several years ago, and he actually offers a kit to upgrade the earlier L5P to the newer oil cooler. That being said, when working the engine hard with high EGT's the engine oil is squirted onto the bottom of the piston to help transfer piston heat to the oil. If oil temps gets much above 220 degrees you better back off because the oil is getting too hot and consumption can go up. I only run 5W40 in the winter when it gets very cold and I can't plug in the block heater because 15W40 offers more protection that 5W40 in most oils. That being said, head winds are a pain, fuel economy drops like a rock and EGT's get much higher because of the increased engine load. I two will drop gears to keep my EGT's in check. I typically drive with my instant fuel economy pulled up on my dash and I will pull the highest gear that gives me the best fuel economy. My engine has on occasion used a little oil, but probably because I worked the engine very hard and got the oil temp too hot. I run 5000 mile oil change intervals and use a good quality 15/40 most of the time. In the last year oil brands have been hard to pin down, but I usually have a years worth on the shelf.