Warning to online car shoppers: One used car for sale on a Facebook profile may be an ordinary case of someone moving on from their longtime daily vehicle. Five or six, on the other hand, could be a bright red flag to be extremely cautious. She also recommends looking for evidence that the owner has lived with the car long enough to know its condition. “Don’t be scared of 100,000+ miles depending on the car and only if they have records of their service,” one viewer wrote. A car with 80,000 neglected miles may be a riskier purchase than one with 120,000 miles and a documented maintenance trail.