what is the best millage to buy a benz or a bmw

Good morning Carprice, Again I agree with Tom. Assuming that you are talking used, I would look for a certified car, and or a car with around 5,000 miles or 5 months remaining on the factory warranty. Or even a car with a extended BMW warranty. Make sure that it includes the electronics, most aftermarket ones only cover engine and drive train, which is usually catastrophic and they don't cover the computers. These beautiful brands are both equipped with sophisticated electronics which in most cases protect the engines and drive trains. If you do purchase one with a warranty, put it through its paces right off the bat for at least the first month. If any warnings or problems shows up, get it into service right away. There are usually some hidden bugs in used cars, but once addressed you should be in good shape with proper maintenance for quite a while. Good luck, Rats