How to pick a route in France?

caracasjim

I travel regularly across France and cannot find a any way to make a decision between RN's and Peage motorways. My route is Roscoff to Angouleme via Niort . I prefer not to use Peage and take the quickest route selected by TomTom but after many attempts I still cannot find a way of comparing a route which can compare high speed Peage against very slow but very cheap side roads some of which never show very
difficult north->south->north manoeuvres on unmanned Peage junctions which are even cheaper
Has anyone else experienced problems on this route???
I take the same route every time and reset the TomTom at various towns on the N10 and check Roscoff to Angouleme in both directions and always get conflicting results .
How can it be quicker to to cover the same distance heading South than it is travelling North ???
unless the TomTom is looking at my performance as a driver as it changes during a long 6 hour drive???
It looks like TomTom avoids the direct route through the center of Niort and tries to make me take the Peage
when the N10 is much better
How can I compare a 100Km 100 minute detour using 15litres on a Peage to save 5 minutes on a RN which is free and only needing 10 litres of fuel to cover the same 100 Km???

cheers

Jim

Niall

@caracasjim

Try using the route planner MyDrive, here are some variations in this link note I have used option to avoid toll roads
The times differ by about minute for the reverse routes, mostly due to the geometry some junctions but also level of traffic is also taken into account