As a newbie I need help, wanting to buy a 7, but MOT mileage shows mileage going backwards at a certain point. Have had a reassurance from seller but generally what do you think. Will the discrepancy affect future saleability? It is a lovely car but should I walk away? When you sell it the buyer may have the same question, but it's really not unusual to replace a speedo on a car like this. So yes, it might have a slight effect on future saleability, but if it's the car you want I really wouldn't let it put you off.