I was over at Cummins Northwest in Portland and asked one of the techs about what he has seen on high mileage of the 5. 9. He told me that he routinely sees a half dozen 3500's that run trailers from Portland to Salt Lake, then to Phoenix, to La then Back to Portland. He says that 3 of them have over 850,000 and one is over 900,000. I asked him what they had done - and they said nothing to the motor yet - and they were running Cummins Blue! Now I'm not sure what we can expect, but these rigs are run long and hard - which is very good for mileage. What's the actual mileage you have seen on a truck? I can't verify these stories - so let's only place mileage we're sure is accurate?