Highway MPG getting progressively worse

[mistermoon]

Over Christmas and new years I drove my '22 PB 2100 highway miles RT between Atlanta and San Angelo, TX. Moving average speed (not including stops) was right at 73 mph. We ran between 75-80 when possible for most of the drive. The trip is mostly interstate with the about 100 miles of 75 mph two lane in TX. My truck is an unmodified XLT 4x4 SC, with an ARE FG topper. We averaged 21 mpg for the whole trip. 27,000 miles on the ODO. We ran in ECO pretty much all the time and using cruise control. The fuel economy has been pretty consistent throughout my ownership. The only thing that seems to hurt is if it's really cold outside, like down around 10 degrees F. I think that's because the battery won't recharge until it's fully above 32 degrees internal temperature. When it's that cold I lose 1-3 mpg depending on the length of the trip.

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[spiritrider1]

Here's a little chronological trip accounting. Just my experience from the longest trip I've taken with my PB.
I did a 1300 mile (each way) N. Texas to N. Dakota trip last year to visit my daughter and grand babies. We were 3 adults, full luggage, truck bed full of boxes, a disassembled crib, and a 6' fully assembled cherry wood and glass curio cabinet. Having the 5.5' bed, it was obviously propped on the tailgate. Not a heavy load but still not 'empty'. It remained in the low-mid 20 degrees most of the trip and moderate to high wind from 45-90 degree angles most of the time. We averaged 17.4mpg going up. 1/3 highway, 2/3 farm-market roads. Worst was through Kansas & Nebraska at 17.2mpg. This is the worst mileage I've ever recorded and attribute it to 87 octane winter fuel blend and sub-freezing temps.
We drove around upper NW N.Dakota (50mi from Canada & Montana) for 3 days and averaged 18.3mpg with 3 passengers and cargo unloaded.
Return trip to N. Texas averaged 21.5mpg. Used 1/2 FM roads & 1/2 highway this time, plus the weather warmed up more as we got further south. Final leg from Wichita to the house was a little over 300 miles and averaged 23.4mpg on the dash. And as anyone knows, the closer you get to home the faster you go!
But I didn't fill up until Dec 5th and by then it had dropped a little to 22.7mpg after daily driving.
Overall for the 2800 mile trip was a calculated 19.3mpg and the truck's trip computer averaged 19.1 on the dash. Some fill-ups were off a little more than my usual .2-.3mpg deviation

but I think that's due to the adverse conditions and the truck is always learning.

Hope this is of value to someone.

 

[dafish]

A few things, in no particular order.

To clear up a few myths stated along the way:

1. Rim size, say 20" to 18" or vice versa, doesn't mean much, if anything, in and of itself. It certainly does no imply a calibration change is required.
   1. As regards MPG, tire rotational mass can be a big deal, particularly in stop and go.
   2. As to calibration, that's a question of tire circumference. ONLY. you can run a lower profile 20" or a higher profile tire on a 18" rim and have matching results. It's common for mfgs to do just that.
2. Tire pressure has little to do with MPG when we're talking about typical truck tire pressure's. Run one down below 30PSI and yes, the implications become more significant. Over 30 and it's harder to see, over 35 and you can't see it outside of very careful testing. And yes, this has been studied many times. MPG increases diminish rapidly as tire pressure increases over the 30-35 psi range. You hear a lot of folks claiming they've tested, but this is mostly observational / confirmation bias. There are several quality lab test results available online if you go look.

Those things aside, I agree taller tires, increased effective rotational mass, and raised ride heights will all hurt MPG.

All of above does not explain OP's experiences. Honestly, neither does "winter blend fuel". Sure, I accept this is a factor, but my opinion, worth no more than you've paid to read this, is that's not it.

I posted a few weeks back a thread roughly titled "MPG, WTH", or similar. I'd rented a Ram 1500 4x4 screw and took it >500 miles to pick up my '22 KR PB. It averaged 20mpg running 78mph almost all the time. The PB didn't make 17, and I went slower. For some hours MUCH slower (serious ice storm). Roughly the same weather, same trip, trucks are close enough to the same weight, for the 150 is aluminum and the 1500 is not.

So yea, winter fuel isn't explaining it. I do, however, have a recently formed hypothesis. First however:

Several have commented that the trucks MPG falls over steeply in the mid 70mph area. Simple physics proves that's not possible. Granted drag is exponential to velocity, so the slope is every increasing, but there should be no cliff or speed where it suddenly gets much worse.

The problem? In this case physics lies, for I've seen it too. Damn things hate head winds, cold, hills, you name, and over a certain speed it all goes to hell.

So what do I think? I think Ford F'd us. Or, to be more clear, I think the marketing liars have too much influence. Then come the lawyers. The engineers? I think we'd have very different results if the Ford engineers could give us what they're capable of.

What do I mean? A rant, then some more science.

I think the tunes we drive are meant to optimize the fed ratings system (see marketing liars), with a second master (lawyers) staying well clear of emissions violations. Actual drivability be damned, be grateful it still starts.

Those that tow know the games we play to stay out of boost, right? Same with hills, headwinds, etc. Why is this? The tunes. I accuse them of pulling timing over det, made worse by lean burn AFR (but it sure looks good on a chart). Poor cam timing. And oh yea, once boost hits they pour fuel in, and hey, let's pull some more timing! Let's not forget they've added LSPI timing retard tables, because they don't know what oil we're using.

So point #1: I think our Eco/power boosts are getting screwed via a lousy tune. In fact, I'm prepared to say a qualified tuner could make major improvements on these.

Now, to OP's experience:

Sir, because of the lousy tune these things come onto boost and MPG goes to hell. Yep, speed affects drag, and so somewhere around 70-75mph we're creating enough drag we're adding boost and realizing degradation far beyond what a non-turbo sees. As I've seen in my rental comparison, as every F-150 coyote owner will tell you, and etc..

So what's making the tunes so much worse in winter? Air density. Air density increases by 1% for every 5f of temperature drop (roughly. It's closer to 4.8f, but...). Air density to drag is logarithmic and I don't recall it anymore, but it's real and significant. Nor can we beat it. Yea, we get more power from increased air density, but we've plenty, we're talking about fuel burn here.

The increased drag from the much colder january (relative to last year), combined with tunes that are ridiculously sensitive to drag and OP's results, as well as mine, come into focus.

The solution? Better tunes, better leadership from Ford, and increased awareness of we owners on things like gear lock-outs, etc (that we shouldn't have to do) to stave off boost and timing retard.

So long post, a few rants, but OP I believe this explains what you're seeing. One guys opinion of course, and surely somebody will object to something (this being the internet and all...).

props to all,

-d

 

[westbayou]

OP here, just thought I'd post an update. My last trip in the 23' PB truck yielded an avg. MPG of 14.8 mpg over 120 miles. That coupled with a variety of electric gremlins and questionable transmission problems led me to trade it in on a 22' Raptor with only 6K miles. On the same trip yesterday with gas from the same gas station, the Raptor averaged exactly 19.0 mpg.

I agree either Ford bamboozled us into thinking the Hybrid would be great on gas, or there was something wrong with that truck. Either way you can't convince me to buy another PowerBoost anytime soon. I'll readily admit the city mpg's were definitely better that the Raptor, but since my time is 65% highway driving I'm not looking back. My 23' truck was definitely the worst vehicle I've ever owned. It had every issue I've read about with the PowerBoost trucks and then some. I should have returned the truck when I had the chance when the transmission ate itself with only 437 miles on the clock. Expensive lesson learned.

Happy ending. I'm back in a Raptor and the truck is amazing.

 

[SteveP150]

I've pretty much come to the conclusion that the PB isn't really any better than the regular Ecoboost at 70+. The electric motor isn't helping much...if you're going uphill or accelerating, the extra weight is likely outweighing any benefit.
A lift/level is definitely going to be worse on mileage at speed. More aggro and/or heavier tires will be worse too. Increased rolling resistance will be worse across the board. Increased weight would show up mostly in acceleration situations.
As others have stated, you're mostly buying this for the power and generator capabilities. Fuel economy has turned out not to be a big plus.

 

[Gord096]

I’m pretty happy with mine.

 

[spiritrider1]

I've chimed in a few times on this thread already but can't help myself saying one more thing...
I drove 33 Farm to market road miles into a steady headwind/crosswind at 71mph on the cruise control just northwest of the Dallas metroplex where land gets flat and there are no buildings to break the wind or vehicles to benefit from their draft vortex except the occasional 18 wheeler. I began the day on a full tank and was around 21mpg on my freshly reset trip meter. By the time I got to my destination I was down to 17.5mpg. I know it would have been worse if I'd gone faster but I usually keep to 71mph which my truck seems to favor.
Now the flip side; after 3 hours I returned on the same stretch of road and same conditions and by the time I arrived where I started I was up to 23.7mpg. Again, I set cruise at 71mph but this time I had a tailwind/sidewind to help. So that was an average 20.6mpg.
Open roads, wind, draft, hills, speed, temperature, load, ... Everything will affect mpg.

 

[Jerome10]

I find winter blend gasoline to drop MPG a bit, also check your tire pressure. Mine were 6-7psi low when I checked them the other day and I noticed a 2mpg increase since airing them back up.

I was wondering about winter blend as well. Plus is it possible the truck can't use the battery as efficiently because of colder weather? Maybe not applicable in Florida....

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