I agree with SJW - we have several cars. The DAB reception in my golf is consistent, consistently ok in some places, consistently dropping out in others, consistently different with different channels, ie BBC national are strong, commercial middling, BBC local stations weak when driving away from them. The time of day, weather, nothing affects it. In our other cars DAB reception is far better, local stations are held onto far longer when you drive away from them, more stations are available.
The only variable for DAB are the station, your location and the different car manufacturers.