I think you forgot to mention it was downhill all the way and you had a 40 MPH tail wind. Maybe your speed was 90 KPH instead of 90 MPH.

Now go the other way and average the two out. Woops.

 

I turn the cruise off when descending long grades or climbing long grades. I leave it on for most HWY travel. I keep the tac right at 1900 which on my truck according to my GPS is about 69mph. I consistently get 18.5 mpg on long trips.
This is with a bone stock engine.
I have the tire pressure checked before I leave on long trips. I run 265/70R/17 tires. I need the cruise on for long hauls because my right leg is bunged up.

 

ways to get great fuel millage

1. Fill up tank and park it ,only use one tank of fuel for the life of the truck

2. load it on flat bed and tow it everywhere . use millage of tow vechiel to figure your milage

3. run downhill with the engine off


all would increase milage . But be real stupid

 

Not only that, it beats the front end and our trucks need all the help they can get in that department. A little cushion goes a long way.

 

They are powerful and built to use fuel, when towing especially mileage is the last thing on my mind. I stay under 65 on the hwy towing but thats about it. I'm getting to that 65 quick.

 

These trucks have a very aggressive cruise, some of you may have noticed that with the cruise set the truck will actually gain speed going up a hill (sometimes up to 2mph on mine). I suggest if you can maintain a constant and steady speed then leave the cruise off and when you ascend a hill (especially a smaller one) allow the truck to loose a little speed and gradually let it return in the decline.
On longer trips, personally, I use the cruise and reduce the POD so the cruise is not so aggressive and when the terrain varies often I turn the cruise off.

I suspect that those who install "tuners" may also see effects on CC function, someone correct me here.

The CC on mine is great. It literally will not slow down for the grades we have along the Gulf Coast. Were I driving in West Virginia I suspect I would have the CC off for some roads, some stretches, etc, as for the reasons stated in the quote.

The Class 8 rigs I've driven did offer benefits in Cruise . . and it never occurred to me to not use it. CC is always "steadier" than the right foot.

I have seen at and above 27-mpg on a number of my roundtrips . . and, while I don't plan to test it (waaay too much work), I do not believe that the right foot will ever match that. As a teenager -- against a dirt-crude CC on a 440 Chrysler -- I had the stamina and energy to beat CC. (But with the advent of computer-control ca. 1980, CC became far more accurate).

If someone is doing back-to-back trips over terrain that is comparable to large areas of the US maybe they'll also be inclined to test CC versus right foot in A-B testing.

My father and I used to discuss this in the early 1970's, and we found that the day-long tradeoff of fuel mileage versus average road speed (time) was small . . but the mental/physical effort was not.