My old Garmin was taking me far off track. It had me on a dirt road which narrowed down to just about one vehicle wide and went up a steep enough hill that I had to use 4x4. It dead ended at a scout camp and luckily I could turn around. It also keep wanting to take me off at every exit and do a left then a right, right, left which would have put right back on the same road and in the same direction.
I had completed the $50 map update package but it didn't work until I reset it. At that point I tested it on an known route it only made two minor mistakes out of five potential choices.
It's tough to work with something that is telling you to exit right and go west when you're supposed to be going east and it changes its mind at the last second while you're pulling a fifth-wheel in traffic.
I use my phone maps at the same time and they will often contradict each other. Just about the time you started doubt one of them more than the other that one will be right.
I look at the maps on my computer and know where I'm going then I let the GPS or my phone guide me along the way. The GPS is very good for looking at fuel stops or fast-food and it will scroll through them as you come upon them.
It's a pricey tool that can help you but there's no way in the world that I would ever set out to go anywhere and blindly follow it.