Currently have a 2007 Expedition with 216k miles that was purchased with 172k. As someone said on this thread, one of the main keys to keeping this engine running is frequent fluid changes. My engine oil is changed every 4k miles and my tranny fluid is changed every 25 to 30k. If the seller is meticulous and knows how to take care of a vehicle, he should have records to show. One looks at the vehicle's condition and maintenance records in an effort to reduce risk. However, let's face it, risk is there on the purchase of ANY used vehicle. You do your research, gather facts and go for it when comfortable. Would not hurt to have a mechanic look at the Expy also. One thing I would recommend, is to have enough cash on hand to handle cam phaser / timing chain repair job. This repair seems to be something that many on this site have come across as opposed to a full-blown engine replacement. Since my timing repair, I have had no issues and the engine has run flawlessly. Remember, just do your best to gather info to make the best choice possible. Good Luck!!!