No issue with idle time at all. When my work truck is turned in at 200k, I'll have the record for idle time. I'd look under the truck. Dents in skid plates? Is the trans nice and clean, or covered in goo?
Service trucks, ironically don't get serviced. So download the manual. If it says timing chains and tensioners at 150k miles, I can guarantee they weren't done and will need done. Since service trucks get used often every day except weekends, they tend to have far better reliability than what consumers deal with. We keep our trucks for 200k, and maintain nothing but brakes and tires. Expect high mileage service trucks to need some joints and tie rods.
If you can swing a 2017, don't look back. Mine is just an XL Fx4 and it's quite nice.
The early 6.2's had a bad batch of valve springs or guides and would blow up exactly when the warranty expired. I think by the end of 2015 that was fixed. 5w30 is the correct oil, ignore the 5w20 on the cap, if it says that. Change the oil every 3-5k. I don't buy into 7.5k intervals at all. You can use 10w30 to tow in the summer. And use high octane fuel in the summer, if it's a flex fuel yellow gas cap truck.
Don't bottom out and bash the exhaust. The 6.2 will bust the header bolts and leak. GM has the same issues. Some people have even managed to crack the headers.
The 2015 grab handles for climbing in, won't support a 230# guy. If I was evil, I'd grab one rip it out, fall on my ********, and sue Ford. Those handles should have a cable or something so they can't just rip free.
The E-lockers are sweet. Absolutely get one of those if you can.
