I don't see any reason that it won't go 300,000 miles. I sold my 1987 Plymouth Sundance Turbo when it was 11 years old with 141,000. At that point, there was nothing to indicate any durability issues. I actually wish I had kept it. If a turbocharged engine could go that many miles 3 decades ago, I have no reason to think one now won 't hit 300k.