2023 Toyota Tacoma SR5/Gears

What does each gear do for the truck?
When do I use each:
1st gear?
2nd gear?
3rd gear?
4th gear?
5th gear?
6th gear?
ECT?
My yearly driving consists of going north to flagstaff from Phx, going east from palm spring to phx, going west to San Diego from phx. This accounts for about 25% of my driving yearly. All three have long hills, my question is what gear do I use for the best results and best gas mileage and the least wear and tear on the trk and I'm not towing anything. The rest of my driving is done in the phx area.
Thanks....

 

1st gear works best at 65mph on the highway, hope this helps

 

Don't overthink it...put it in D and drive it. If you feel the need to downshift, slide the shifter over and manually change gears but otherwise, just drive the truck.

 

From what I feel like during ECT button, it feels like it skips/jumps gear faster. Instead of holding on too long in same gear