Punchingclowns

I have a 2015 F150 3.5l Ecoboost. 3.55..

I use the tow mode when hauling to the gulf to launch. I am taking a trip soon and it will 450 miles of mainly I-10. Once I am on the highway and moving like normal is switching off the tow mode going to help my gas mileage? Will cause any stress on the truck with it off?

Thank you

Ricktwuhk

No, it is unlikely to help your gas mileage. No, it is not going to cause any stress.

You should use it.

marshallr

My owners manual says to switch off the tow haul mode when on level roads to improve fuel mileage.

Ricktwuhk

Mine says exactly the opposite:

When Towing a Trailer
• Do not drive faster than 70 mph (113 km/h) during the first 500 miles
(800 kilometers).
• Do not make full-throttle starts.
• Check your hitch, electrical connections and trailer wheel lug nuts
thoroughly after you have traveled 50 miles (80 kilometers).
• When stopped in congested or heavy traffic during hot weather, place
the gearshift in position P to aid engine and transmission cooling and
to help A/C performance.
• Turn off the speed control with heavy loads or in hilly terrain. The
speed control may turn off automatically when you are towing on
long, steep grades.
• Shift to a lower gear when driving down a long or steep hill. Do not
apply the brakes continuously, as they may overheat and become less
effective.
• If your transmission is equipped with a Grade Assist or Tow/Haul
feature, use this feature when towing. This provides engine braking
and helps eliminate excessive transmission shifting for optimum fuel
economy and transmission cooling.
• If your vehicle is equipped with AdvanceTrac™ with RSC, this system
may turn on during typical cornering maneuvers with a heavily loaded
trailer. This is normal. Turning the corner at a slower speed while
towing may reduce this tendency.
• If you are towing a trailer frequently in hot weather, hilly conditions,
at the gross combined weight rating (or any combination of these
factors), consider refilling your rear axle with synthetic gear lubricant
(if the axle is not already filled with it). See the Capacities and
Specifications chapter for the lubricant specification.
• Allow more distance for stopping with a trailer attached. Anticipate
stops and brake gradually.

humblerb

Just an educated guess, but I don't think it will have any effect. Once you are on I-10 you are on fairly flat terrain. The vehicle will settle in its comfort gear and you will be OK.
TH assists in holding a gear longer to decrease the amount of searching for gears, which overheat the tranny.
Once you are on the flat and maintaining your speed, I wouldn't think it would have much effect at all.
Leaving it on shouldn't affect mileage as long as you are able to maintain a speed and a gear.

Jus Cruisin

Y'all will be on a nice flat piece of interstate and you will end up in 6th even using t/h. If I'm towing, I'm in t/h.

Aj06bolt12r

Always use tow haul when towing. I would also suggest locking it out of 6th gear so the highest gear it can reach is 5th. This will help keep everything running cooler and eliminate a lot of shifting between 5th and 6th.

I also feel like it is just easier on the engine. Right around 2000 - 2400 seems to be a sweet spot for these engines. Lugging it down below 2000 while towing just does not feel right to me. Its easier on the engine to run a little higher RPM with less throttle open percentage and less boost than it is to lug along at low rpm with more throttle opening and more boost.

I actually think this nets better overall fuel economy as well, for the same reasons. Less lugging and throttle opening before finally downshifting to recover the speed you could have just maintained had you already been in 5th.