That is a very valid question. You actually cannot, you have to trust who you get your motors from. I buy all of my motors from one place. It is a trusted private dismantler. That is the tricky part of this. My supplier tells me when one is over 100k and the price reflects it. Another way of getting a good idea is to look at the physical condition of the engine. It's pretty obvious when one has been pressure washed, so if it hasn't been cleaned and is still pretty clean, it's a good indication that the supplier isn't lying about the mileage. My dismantler is a one man operation and he removes all the engines himself.
