I’m not aware of anybody doing “eco friendly” routes with the intelligence, scale, or impact of google maps. Sure, it’s not a sexy cool thing, but it’s important.
For most cases, minimizing energy means minimizing accelerations (positive or negative). I think that's usually the same route that minimizes time, and that's how most roads are planned: as steady as possible traffic flow. In most places I've lived, there seems to be an intentional penalization going off the "main" road, with stops signs at every intersection, so you don't drive through the housing areas.
Do you mean routes that might avoid great elevation changes or something?
Shortest route is usually most fuel efficient, but in some cases it will surface a route that is three min longer but uses less energy for whatever reason.
I tried the eco friendly routing on a few softwares; I think https://maps.openrouteservice.org does it and our car also. In both cases, it turns highway traffic into city and B-road/Landstraße traffic.
This is counter-productive: it produces more CO2 for all the braking and accelerating.
What you need to do is don't drive 130 but drive 100 on the highway. Go behind a truck if you are okay with going that slowly (not to avoid wind, afaik then you'd have to be unsafely close, but behind a truck you cannot annoy other people because they need to overtake the truck anyhow). The downside: on an average commute of like 20 minutes, that costs you probably like 2 minutes extra (since top speed is far above average speed usually). The upside: your fuel consumption (fuel burned = CO2 created) is cut nearly in half, at least for the highway part of the trip. No braking also means less particulate matter from brake wear; no shifting back means less partial combustion. Or so I've read.
The most efficient speed (afaik): as slow as your car allows (~1000 rpm) in the highest gear it has.
I hope it goes without saying, though, that one should prioritize safety (go with the flow; worse/more(?) accidents happen in high speed difference zones) over efficiency gains.
Our EV likes to suggest a route that takes 33 minutes instead of 28, but uses 30% less electricity (and avoids rush hour backups, as a bonus). It's using HERE WeGo maps, from what I can tell. (They're underrated in my opinion. They're formerly known as Nokia Maps; it was the default on windows phone, still is free phones, and still works offline.)
"Eco friendly" is a function of the car's aerodynamics, weight, regenerative breaking, auto shutoff at traffic lights, etc, etc. It seems better left to the manufacturer to set those parameters.
Walking and biking are much more "eco friendly" than saving some fuel on a car ride, yet google maps has no idea where the bike lanes are half the time.
