Millions in the UK sell cars hiding known issues to save on repair costs, risking road safety. One in seven drivers admits to such sales, with millennials being the worst offenders. Common undisclosed problems include weak batteries and faulty engines, leading to potential MOT failures. Despite valuing vehicle history, many neglect detailed checks. Trust still lies with dealerships, but private sales lack confidence and transparency. Buyers often face repair costs and lack knowledge to spot faults, highlighting a generational gap in honesty and awareness in car sales.