I am over a year now on my 6.4L RAM. It never fails to bring a smile to my face.
This year we got a new Cougar 339BHS 5th wheel. It's about 12,000 lbs loaded with 2k pin weight. The 6.4L with the 4.10 gears handles it with ease. A buddy of mine that owns a transport company has towed thousands of RVs had told me that my new 5th wheel would be easier to tow than my 8K travel trailer. I was skeptical...but after a few long trips I have to say he was 100% correct. The 6.4L handles it easily...I use cruise control set on 60 or 61 mph. My engine runs in 5th gear at about 2100 rpms...the engine is able to hold 5th up small inclines, but on the bigger hills it will downshift to 4th, run up to about 3000 rpms until it crests the hill and then shift back into 5th. It pretty much stays between 2100-3000 rpms at highway speeds. In other words...it's not working very hard to pull that 12K trailer!
I have a Curt hide a ball gooseneck and the aluminum Andersen Ultimate 5th wheel connection. The ride is solid and smooth as can be. I am EXTREMELY happy with this combination...especially the truck.
I do the oil changes myself with WIX filter and Mobil 0w-40 from Wally World. I wait until the indicator tells me I am at 25% remaining oil life and then I start planning to change the oil. I did the initial oil change at 1000 miles though...I am at about 12,000 miles, with 4000 of that towing. I drove the truck a lot the first year. I don't drive it nearly as much now. Basically I only use it for towing or driving if the wife's car is not available (a Chevy Volt, GREAT car...averaging 115 mpg since we've had it (over 1 year)). So from now on I'll probably only put about 6K a year on it.
Its the only vehicle that I've ever bought that I have 0 buyers remorse. I LOVE my truck...so much that I don't even like other people working on it :-) I took it to have the tires rotated last weekend and I was nervous as hell about those guys driving it, lifting it, torquing lugs, etc. I used to work in a garage...I've seen many vehicles lifting incorrectly. I've also seen morons breaking studs, stripping studs, forgetting to tighten lugs, etc. I've seen enough to know that I prefer to do it myself so that it's done right....anyway GREAT TRUCK! Very happy with it...that said...my next one will be a Cummins :-) I don't need it...I just love diesel engines and I want it!