I just recently had my gps get me to try and drive down a gravel road (not that bad) and through a ford that was clearly far too deep for my car, and had a sign on it saying that it was unsuitable for cars, all to save about a minute.

Google maps also doesn't seem to know whether roads are gravel or tarmac, and since they both have a 100 km/h speed limit, it will direct me down a shorter gravel road, that will actually take longer because I'm not suicidal to go 100 km/h down a windy gravel road.