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Right, you arent grocery getting so change it at 20k. It doesn't say etc, it says frequent towing. They do leave the determination of frequent up to us. Are you frequent or am I frequent? My money says I'm towing more towards what a ctd is designed to do so 20k. Don't change it at all and you will probably be fine. If you do have the truck long term and the set or the carrier bearings go out you will only be able to wonder if changing could have prevented it. If those who do change at 15 or 20 or whatever have a failure they will know it wasn't from a lack or changes. If they use the spec oil they also know it wasn't the oil.
The other issue I see regardless of what any manufacturer or you or I or anyone here thinks, it only takes one time of hitting the Eisenhower tunnel or east bound from Vail on 70 to put the hurt on the oil with 26,000 pounds going through the gear set with 28 pounds of boost.
I've heard of smoking drive axles in that territory.
I'd be happy to have a gear failure compared to a diesel issue but I do error on the side of caution or overkill with all these systems since it's very inconvenient to be broke down."
I agree with everything you said.
But I'm sitting here at 30K with the OEM lube because nowhere in the manual it says I need to change it now.
I'm not a frequent tower, not a Police car, not a Taxi, not an Ambulance, etc..
Bottom line is I'm gonna change it yesterday.
