Pretty sure it's for new cars only. I've found out that when my free trial year of the Transit tariff expires (18th August 21), Audi are basically saying that the card should be destroyed. I've gone back to ask them if I can transfer to the City tariff fro a month or 2 and use up the spare credit, but no reply yet. Failing that, I'll have to use DC chargers to run it down as I won't be doing a road trip due to excess mileage costs!!!