Not with modern turbo diesels. EGT temps can change pretty fast, once you get too hot you need too slow down and downshift to get more cool air flowing across the pistons. The stock coolant gauge is not really a gauge as much as a glorified idiot light that by the time it shows too hot the damage has been done. A good after market coolant gauge will help some but will not tell you what is going on inside the combustion chamber timely enough to be proactive.
I would tend to agree that a totally stock impeccably maintained truck is designed to not exceed the max egt temps, whether yours actually does or not is the question and there is only one way to know, gauges.

 

Well it sounds to me like you think TQ has something to do with towing performance but as I discuss below it's really only the HP that counts and setting your "cruise at peak torque" is a bad idea!

In a given gear MPH is directly proportional to RPM which is written as MPH~RPM. To maintain a constant MPH* at RPM* on a level road you need enough HP* to overcome the aerodynamic drag and rolling resistance at that MPH*. So on a level road the cruise control applies just enough throttle to produce a BP* at RPM* to make the HP* that's required to cruise at MPH*.

If you now come to a given %Grade you need an additional HPg~(%Grade)(GCW)(MPH*) to climb the grade at MPH* and the cruise control then applies more throttle and if the engine can increase the BP enough at RPM* to increase the HP by the additional amount HPg then the truck will climb the grade at MPH*.

If the engine can't increase the BP enough at RPM* to increase the HP by the additional amount HPg then the PCM will command a downshift to increase the RPM to a value higher than RPM* which will get the required additional HPg and the truck will climb the grade at MPH* but in a lower gear with an RPM higher than RPM*.

If you set the cruise control on the level road for an RPM* that's equal to the RPM for maximum TQ and then come to even a slight grade which reduces your MPH slightly below MPH* and therefore your RPM slightly below RPM* your available HP to climb the grade which is HP~(TQ)(RPM) decreases rapidly because both the RPM and the TQ decrease and this increases the likelihood of the PCM commanding an immediate downshift before the BP can build to provide the needed increase in HP.

The best strategy for towing is to cruise at several 100 RPM above the RPM for maximum TQ so that when you come to a grade which slightly reduces the RPM the TQ will increase and the HP~(TQ)(RPM) won't decrease by nearly as much as when both the RPM and TQ decrease!

I think the best MPG strategy for towing is to not use cruise control because trying to maintain a constant MPH over even slightly varying terrain isn't fuel efficient. It's better to look ahead and let your MPH increase some on the downgrades and decrease some on the upgrades because this minimizes downshifting which isn't fuel efficient. In other words let gravity work for you on the downgrades and don't fight it as much on the upgrades!

The HP that's required to overcome aerodynamic drag is HPd~MPH^3 so if you reduce the MPH a little on the upgrades you can save enough HPd to supply the needed HPg without needing to downshift as often.

The reason why towing at several 100 RPM above the RPM for maximum TQ works to your benefit doesn't really having anything to do with TQ per se but rather it's all about the "shape" of the "HP vs RPM curve" and operating at a point on this curve where the HP doesn't decrease as much for a given decrease in RPM.

 

Thanks for all of the input!!
What you stated above is exactly what I do with any hills. My strategy is to increase speed on the down hill to avoid a downshift on the up hill and it works quite well with the PSD. I am pretty much only using the cruise on flat stretchs and will let it carry me over slight overpasses once in a while. With shorter trips I won't use the cruise at all.

 

That makes good sense....just one more to add to the list!
Thanks!

 

Thanks Gene. Thats what I said, you just used a few more words then I did.