Jon, I'm using Lucas in my truck. Biggest priority for me is keeping some lubricity in the fuel to nurse the injectors. Read a few lube tests and the Lucas isn't the top pick but it isn't bad and my truck is happy with it. I use to run the TCW3 from Walmart for the price but the truck didn't like it much. She felt sluggish. As far as mpg, the biggest factor is driving conditions. The truck likes to roll. Efficiency in our trucks takes a huge hit from stopping and starting in the city life. But I'm at 14-16city depending on how I've behaved while driving. Highway bumps to 16-20 depending on conditions. Biggest factor, how I drove it.
As for a programmer, I'd like to get into EFIlive. But if I do I'm going to get into the Pay to Play game and I just don't want to start. It's expensive and there are other things I want my disposal income going to right now.
I'm about 500mi from an oil change myself (7500mi interval). What oil and filter do you go with? I grab filters a few at a time (Fleetguard 16035) and keep 3gal of Valvoline Premium Blue, Mobil Delvac when they go on sale for 9.99-12.99. Keeps the cost reasonable. I do send off an oil sample for analysis. Also a way to keep tabs on the injectors & cylinders (by the fuel content). I'm pretty confident in the internal health of the motor with this maintenance.
I will use Rotella or Delo. The problem with Rotella is it smells, hence the "Rosmella" nickname you might have heard about. It OAs fine, just smells strong when the truck is running.
If u look at the back of the bottles it meets or exceeds manufactures rec I have run it since day one. No issue's other than turbos being replaced. And before someone says something the turbos on a 6.7 Cummins is coolant cooled not oil cooled
5w40 works great for start ups in cold cold weather. IMO a synthetic isn't necessary, and I say that based on the results of my OAs of 15w40 oils. If you are planning on running extended intervals, I'd suggest an oil bypass kit. In our truck's oil it is the insolubles (soot) from the 3rd injection event that are the issue. From there I'd walk up the interval to the limit of a quality 15w40 (based on OA results). If I wanted to go higher, then jump up to a synthetic in addition to the bypass kit.