Too much mis-information about..
Currently vehicles imported from non-EU countries have a 10% tariff applied (less for Japanese made cars because of recent EU trade agreement with Japan). If we leave the EU without a trade agreement that same tariff will apply to EU manufactured cars. As I argued earlier that does not mean prices of EU made cars will rise by 10%, it’s up to manufacturers and importers what price they charge. UK made cars will be unaffected by leaving the EU and there is no reason their prices should rise.