When I’m towing my fiver, I like to keep it in tow/haul for the engine braking via downshifting. If I need to hit the brakes and stop in a hurry, I can focus on the situation as opposed to trying to find that small shift button.

Otherwise, there’s no other real advantages. The owners manual actually suggests turning it off on flat ground when at cruise speed to increase fuel mileage.

 

tow/haul uses a lot more DEF.

You didnt mention towing anything, so what scenario are you manually shifting?
I assume you are going down a grade and trying to slow the truck

 

What’s DEF? 😀😀😀

 

Curious why tow/haul uses more DEF. I assume the DEF injection rate is correlated to engine RPM? Other than holding gears a little longer during acceleration, how does tow/haul impact the DEF usage?

 

Using the toe/haul increases the rpm shift points. The higher shift point has more fuel going through it so you get more soot in the exhaust. More soot means more DEF to burn it out.

On flat land I will not use the tow mode when I have an empty gooseneck. It gets better fuel mileage. Any load or hills I will have it in tow mode.

 

The biggest difference between manual mode and tow/haul, is your torque converter lockup schedule. For example- stock tow/haul will not go full lock in 1st gear, manual mode it goes full lock over 7mph. Same thing with tow/haul vs normal. This is the other major factor besides rpm, that effects fuel mileage/def. TCC lockup increases load, which increases fuel demand, which increases soot, which increases def usage (if stock).

 

DEF burns off soot? I dont think thats correct

 

Who said it does?