Research by the website claimed the average car showroom finance deal charges 10 - 12 per cent in interest - 4.22 percentage points over the best loan deal. It said drivers are set to waste on average £1,200 on cars with the new 2007 number plates. “A rushed decision or just taking the finance deal offered by the car dealer could turn out to be a long-term financial burden," explained Nick White, uSwitch director of financial services.