I would think one of the questions you should ask when looking at buying a used audi is "what is the oil consumption of this car". Also ask if this car has had the oil consumption test and if so what were the results. Then you would want to know what corrective actions were done . The other stuff such as paint and interior and entertainment system is all visual. The drive gives you some indication of it's condition. Now if you are serious about getting the car and paying $20-$35K for the car I would ask the dealer to perform a consumption test to verify the engine is OK. If they won't do it or give you a written statement of it's condition then I would not buy it.