It works off the interior temperature that is set by the climate control as well as engine sensors. If the cabin is warm enough that heat isn't required, then it will shut down, same in the summer if it is too warm.

 

I recall back in the '70's when Cruise Control (sometimes called Speed Control by some) was becoming popular. Mopar owned Perfect Circle (Piston Ring makers) that developed a very good control and of course Mopar used it just like PC made it and it worked well for them. GM came up with their own that was just junk but they hung in there with that junk for years anyway, oblivious to how bad it was.. Ford, out in the cold with regard to Cruise Control. went to Mopar/Perfect Circle and licensed the some Patent rights and the ability to improve on them, and they did putting a usable Cruise in that you could 'Beep' up and down in 1 MPH increments. The best available by the early '80's.
This Start/Stop feature along with reducing cylinder(s) ignition seemed pioneered by AC Delco in the early '80's with limited success. Eventually it kind of worked, I don't know who got it right first or even if anyone has yet. I have only driven a GM rental and I hated it. I understand it can be turned off on Ford products which causes me to think that it might work better in Fords. At least I am less dubious about buying a vehicle with that feature if I can disable the feature on my own.

 

The primary purpose of EPA fuel economy estimates is to provide consumers with a uniform, unbiased way of comparing the relative efficiency of vehicles and the EPA's test procedures are designed to reflect real-world driving conditions, no single test can accurately model all driving styles and environments, differing fuel blends will also affect fuel economy, the use of gasoline with 10% ethanol can decrease fuel economy by about 3% due to its lower energy density and EPA tests are done with ethanol free gasoline.

The EPA rating for combined mpg presumes that we drive 55 percent of the time in the city and 45 percent of the time on the highway. Most people simply assume that's the case in their own driving. But many motorists — especially those in urban regions with lots of traffic congestion — spend far more time driving in city conditions than they do on the open road.

It's also useful to remember that even when a lot of driving time is spent on a highway or freeway, it only counts as highway driving when the average speed is 50 mph or so. Crawling toward Manhattan on the LIE (Long Island Expressway) at 20 mph is actually city driving, even though it's technically done on a highway.

If you diligently keep track of the number of miles that you are really driving at highway speeds each day for a month or so, you might find that you really are doing most of your driving at less efficient city speeds. If you have a newer vehicle with a trip meter that displays your average speed, keeping track is easy. Just set it to zero each morning, and then check each evening for your actual average speed for the day.

There are too many variables to say that you are going to get the EPA numbers in your truck or car and the statement on the vehicle's window sticker-
"Your Mileage May Vary" is 100% correct.

 

If driven to the EPA standards you have a 99% chance of falling within those numbers. I haven't done it with my current truck, but in the 2014 I had, if driven at 55 MPH, it exceeded the EPA ratings. If you maintain an average speed of 48-51 MPH then EPA highway ratings should be very close if not better. You cannot expect to get any where near EPA if doing 70 or faster, and unfortunately, way too many people complain about poor MPG while doing 70+. EPA is a Sustained speed of 60 MPH with an occasional burst to 80 to simulate passing on a 2 lane. This pretty much describes my daily drive to a T. Also keep in mind the EPA does not use Interstates as Highway, but rural 55 MPH 2 lanes as highway. The vast majority of highways in the US are just such roads.

Once a person understands this, then the EPA ratings make much greater sense.

That is some interesting information regarding the Cruise Control. I remember back in the late 80's installing my own Cruise control system from JC Whitney. It had magnets strapped to the drive shaft, a pickup that mounted near the magnets, and a vacuum servo that connected to the brain box and the throttle. Now the Cruise in my truck searches for vehicles ahead of me and brakes and adjusts speed to match. Using Cruise I get the best MPG that I can, driving without it I either find myself slowing too much or going too fast due to the roads I drive on, hilly, curved, and with cruise on, much more relaxing.

 

EPA: 23 mpg combined
Typical F-150 Owner: (after upgrading to larger wheels and all terrain tires, knows only 2 speeds - 0 and 80mph) EPA lies! I'm only getting 12 mpg on this thing.

I've got a 2016 XLT Sport with the 2.7 ecoboost and I average 21.5 mpg over the last 2 months. For a full size truck, I'll take that!

 

The 3.5 EB does pretty good at 70 MPH too.



Here is my last tank

log Date miles gallons MPG Price
44 4/21/19 419.50 17.308 24.24 2.639

My mid trip had a lot of city driving mixed in so only got 19 MPG, but for the entire trip i averaged out to 22 MPG.


My dash read 806 miles to empty when I filled it yesterday.

 

acdii,

Did you do anything to your truck to get that kind of mileage? I traded in my 2016 for a new 2019 3.5 Ecoboost Platinum, and i have been utterly disappointed in the mileage....My first trip out to the Farm with it i got 13.9 MPG on the interstate doing 80, and i got 15-16 when i got on the back highway doing 70. I thought for sure that with the 10th gear that I'd be seeing better mileage than my 2016, but it's not even close. Part of the problem is my Turbo is always engaged at 65-80mph. Is your Turbo always on? I've been wondering if it some sort of issue that I need to get re-programmed.

 

Mine is RWD for starters, I have a topper, and always use the cruise control. I also keep it to 74 or less on the Interstate and 60-63 on rural highways. Other than a few tanks, I consistently have been using Mobil 87. I drive somewhat conservatively, but I don't granny it (then again if you saw my mom drive, who is a granny, that term goes far far away). I have fun, but not too much.

Now my last truck, what a POS it was, got about 18 on a good day, it was a Gen 1 EB 4x4. It did poorly on the Interstate like yours. No matter what I tried, even with 5* tunes, I could not get decent MPG out of it, but the 2014 I had, which again was RWD, got pretty consistent 19-20 MPG.

I don't know if it is because it sits lower, weighs less, is more aerodynamic without the front drivetrain causing turbulence, or what, but both RWD trucks got better, more consistent MPG.

 

On my 2006 Ford F-150 XLT supercab 5.4L 3 valve 2WD, I get around 9-11 city and 15-17 highway, sometimes getting 20-22 while driving in slow (35-45MPH) curvy mountain roads. (like around Mount Rushmore)

What amazed me, is that I tend to get the higher mileage when I have a loaded bed.

 

I have lost as I calculate it about 19% in fuel mileage both combined, and highway. Seems like a big difference to me. It just came out of nowhere and has been going on now for around 4-5 weeks. I have done the usual things, tire pressures, new air filter, injector cleaner, better gas. And nothing has helped. Contacting my dealer, even though I know the service Mgr., and he is a good guy, he gives me little hope in being able to track down the problem as it is not throwing any codes. If anybody else has gone through this...please give me some info. It's a 2014 F-150 SCAB, 5.0 L, no mods. Stock size tires. Low miles, about 37,000.
Anyone? Bueller, Bueller?....