I have 304,000 miles on my Explorer. Replaced the transmission at 290,000. Replaces heads (cracked) a year ago. Dealer told me that there was no "gunk" in the heads which meant the motor runs clean. This car has raised two children and has been phenomenal! Plan on trading it in on the Ford Edge in a few days. Hard to see it go but I'm ready to get better gas mileage.