choose the eco route and enjoy the fact you will use less fuel
You must have a different satnav to me!
Mine is a TomTom Go6200Professional (so it accepts dimensions etc).
Try "driving" from Soria (Spain) to Almazan (as I did after a long day, getting off the ferry at 8am).
There is a perfectly adequate, smooth two-lane dual carriageway BUT Tomasina directed us off it a J56 onto a forest track with boulders and fallen trees to rejoin it at J44.

That despite it being set to "avoid unpaved roads".

Give it a try and see where you get taken!
Gordon
It doesn't do this on truck or bus mode, just car & van.
Fortunately I know what "camino" means in Spanish so I never actually took that route, but could see it from the main road, which she was happy for me to follow once I rejoined it. [Hence my comment about boulders and trees.]

It also took us through small villages with traffic lights, roundabouts and cobbles despite there being by-passes (which were visible on the screen).