SatNav Eco Route

[Trewithy]

Does anyone use SatNav Eco Routes.  I went to visit my daughter in Bristol and when in the city I used the sat nav quite a bit which I always have set on the fastest route.  My daughter wasn't impressed with the routes it selected and I have noticed in the past some of the directions didn't seem quite right.  When I got back home I mentioned this to a friend who suggested I try the Eco Route setting.  He said  eco routes tries to keep you on main roads where you can maintain a steady speed.  Has anyone tried to compare fastest routes against eco routes?  I know I could use Google Maps or Waze which are better but I specifically want to know about the sat nav in the car.