ast weekend I undertook a longer tour (approx. 600 km) navigating with the app. Data consumption: 430 MB. Before each trip, I checked via WLAN whether I was using the latest offline maps. Of course, I don't want to navigate in offline mode, as I would then miss out on the traffic information.
I also noticed that at higher speeds and in the mountains in particular, the map often makes very large jumps, i.e. moves jerkily.
Alternatively, I have used Sygic as a navigation system and I get about 10-15% of the data usage.