MPG at 75-80 MPH?

My long term MPG is sitting at 26.7, mix of city and highway driving, with typical commute being around 5 miles in the city and 20 on the highway. I usually do around 75-80 on the highway.

EBM Premium with PP, 6A, full bolt-ons, tune, turbo (VS2+), and WMI.

At 75-80 mph, I usually get about 26 mpg. Manual transmission, 3.31 gears, 20" wheels, Cobb tuner set to economy mode.

Bull Run said:

My long term MPG is sitting at 26.7, mix of city and highway driving, with typical commute being around 5 miles in the city and 20 on the highway. I usually do around 75-80 on the highway.

EBM Premium with PP, 6A, full bolt-ons, tune, turbo (VS2+), and WMI.

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I'll bet your car takes forever to warm up on those frigid, Arizona mornings... :lol:

One of my trip meters has never been reset since new. 21.5 mpg combined over 18,000 miles.

22mpg hwy for your car is not good.

I got 28 mpg on a long run of highway at 75 mph.
probably 100 miles of straight road.

Chef jpd said:

I got 28 mpg on a long run of highway at 75 mph.
probably 100 miles of straight road.

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Wind? Hills? Indicated mpg or measured? My indicated mph is consistently 2 mph less than measured.

Something has to be wrong for my mpg to just tank like this. I drive 13 miles highway and 7 miles city every day. I'd think I would get 25-26 not 21-22.

Base auto 3.15 gears. Deleted AGS, ETS intercooler, Airaid MIT/AEM dry filter, off road DP, lowered with stock 18s and spacers. I drive 5 miles 1 way to work. I let the car warm up for 5-9 minutes average every morning. 1 stop light and 1 stop sign. I average 22.3 on the dash.

TorqueMan said:

Wind? Hills? Indicated mpg or measured? My indicated mph is consistently 2 mph less than measured.

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pretty flat terrain, no appreciable wind.
this was with cruise control on. indicated speed was within 1 mph of the Waze meter.

Ebm said:

Something has to be wrong for my mpg to just tank like this. I drive 13 miles highway and 7 miles city every day. I'd think I would get 25-26 not 21-22.

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IDK, a lot of what you're saying makes me believe there's nothing wrong.

--A significant portion of your driving is on a cold engine
--A BIG drop in the amount of highway miles (since you moved)
--Driving on the highway in 5th instead of 6th
--Winter

The two biggies (to me) are the change in temps and the drop in highway miles. 13 miles on the highway is just about enough to bring the engine up to normal temp, especially with the colder temps. Until the engine reaches normal operating temp the computer will run a rich mixture, and your mileage takes a hit. It's even worse in city driving.

Take a longer trip on the highway and see what happens. I'm betting you won't see a significant difference from what you used to see before you moved.

TorqueMan said:

IDK, a lot of what you're saying makes me believe there's nothing wrong.

--A significant portion of your driving is on a cold engine
--A BIG drop in the amount of highway miles (since you moved)
--Driving on the highway in 5th instead of 6th
--Winter

The two biggies (to me) are the change in temps and the drop in highway miles. 13 miles on the highway is just about enough to bring the engine up to normal temp, especially with the colder temps. Until the engine reaches normal operating temp the computer will run a rich mixture, and your mileage takes a hit. It's even worse in city driving.

Take a longer trip on the highway and see what happens. I'm betting you won't see a significant difference from what you used to see before you moved.

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OP also said he put 20" 275 width tires on the car...the 275's give you a wider contact patch (=more rolling resistance=lower fuel economy). Also, if he changed the tire diameter, and the PCM wasn't reflashed to account for the new tire diameter, there's a good possibility the speedometer/odometer/trip computer are all reading innaccurate here.

I tend to get better gas mileage above 70MPH in 5th gear (28.4mpg average) I am running 3.55 gears, one piece DS and balance shaft delete on 19" GT PP wheels with Sumitomo Ultra hi po AS tires 275s all four corners (275/40s) on custom tune+ 93 tune. In 6th gear I am averaging 26.8 above 40 degrees and 24.8 below 40. With the denser colder air you loose a few mpgs. During the summer I average 29.7 to 33 on the highway depending on speed between 68-80 mph...

ElAviator72 said:

OP also said he put 20" 275 width tires on the car...the 275's give you a wider contact patch (=more rolling resistance=lower fuel economy). Also, if he changed the tire diameter, and the PCM wasn't reflashed to account for the new tire diameter, there's a good possibility the speedometer/odometer/trip computer are all reading innaccurate here.

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The PCM does not need a reflash for tire size, since 2015 Ford now calculates based on the ABS module for tire ratios/speed and its automatic within a range now (min/max %). Previously it was based on the speed sensor on the transmission and the PCM. That is why if you stay withing the min max range on tire sizes you most likely do not need to re-calibrate the PCM now for the speedometer change as long as you are withing tolerances. The same goes for gear changes. If you upgrade your gears or tires but do not go crazy you are good. For instance going from 3.31 to 3.73s will prob be ok but 4.11s or 4.56s will be out of spec and may need a reflash, same goes for the tires. IF you go from say a 255/40/18 to a 255/40/19 or 265/35/20 you will be ok with the speedo, but if you go 285 or 295s on the fronts in a 40 sidewall, you may need to flash the ABS to make up the difference.

Also if you do go out of spec you will need a special flash tool to even make the corrections, which oddly enough is sold by Whipple. =)

Can you do a test of about 20miles on the highway on cruise? I believe that way we’d have a good baseline to give you our results. I think you should be at least 28mpg without a tune assuming you putting 93octane. I’m not familiar with cold weather/engine effect. When was the last time you check/changed plugs?

My cluster reports 26-27MPG on my normal commute to work (4.5 miles, 1-2 stop signs, two lights, and four. Turns). Since switching to winter tires and winter gas, I’m down to about 24.5MPG. I typically start coasting well in advance of stopping and don’t accelerate too hard.

On the highway cruising at 65 I can get 37-38MPG. If I cruise at my preferred 78 on the interstate, it goes down to 32-33.

2017 Ecoboost Premium MT, 3.31 gears, 235 tires.