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Old 08-25-2017, 08:46 AM   #1
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2017 F150 3.5 Eco - trip computer MPG 10% high

Just returned from our 'eclipse trip'. I always track my vehicles on a spread sheet. The trip computer on the F150 showed 1476.7 miles and 12.8 mpg.
From the fill-up very shortly before trip to fill-up when trip finished:
1510.3 miles (from odometer readings), 127.25 gal gas for 11.87 MPG.

We did hit some minor grades (Cheaha SP in AL, Cloudland Canyon SP in GA, Tallulah Gorge SP in GA) and did a bit of sightseeing w/out AS (Table Rock and Caesar's Head in SC, Cloudland down and back to Chattanooga).

Surprised at this big of a discrepancy....anyone else see almost 10% difference between trip computer and actual calculated MPG?

BTW - never towed before so nothing to compare to, but really pleased with handling of the F150 with my 26U on the trip.
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Old 08-25-2017, 09:46 AM   #2
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Did you reset the mpg calculation at the start of the trip?

Apart from that, all on board computer mileage readings are subject to error. True mpg is calculated from fill to fill, measuring fuel added, or even better, over multiple fills.
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Old 08-25-2017, 09:56 AM   #3
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In our last Ford 2015 Transit van, and the current 2017 Transit, the computer is uniformly high by about 1 MPG, and the posts on the Ford forums agree.

No big deal if you can accept the discrepancy. Who knows what kind of algorithms they use? It is probably the marketing department forcing the MPG stats "up" as a way of boosting sales!

Not worth fussing about IMO.

Good luck!

Peter
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Old 08-25-2017, 10:03 AM   #4
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Yes, reset at start of trip (hence about 34 mile difference between trip computer and actual fill-up milage.)

Agreed not worth losing sleep over! Also, maybe pressure from marketing dept to run the computer a little 'high'.
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Old 08-25-2017, 10:09 AM   #5
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Glad to hear you like your truck and trailer combo. The 26' Flying Cloud is a nice floor plan. When we return to Airstreaming, it will most likely be in that floor plan.

On the subject of mileage, does your truck show the same discrepancy when not towing?

I used to tow a 28' foot International with a 2007 Chevy HD diesel. Always filling to the top of fuel neck, my indicated mileage was usually .1 to .2 tenths higher than calculated mileage.

See attached web site: Ford, GMC, Chevy, Dodge, and Toyota trucks tested in a towing match up. The testers were surprised in a slightly negative way with the eco boost fuel economy.

http://news.pickuptrucks.com/2016/01...eage-test.html
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Old 08-25-2017, 10:45 AM   #6
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What's almost more interesting to me is that there is a discrepancy between your trip computer and the odometer mileage (1476 versus 1510).

Many vehicles have a fixed odometer, a resettable trip odometer, and a trip computer. In all the vehicles with these functions that I've owned, if the trip computer and trip odometer are reset at the same time they will record miles identically, and these miles are then accumulated to the fixed odometer.

In my 2017 3.5 Ecoboost there is no resettable trip odometer; the trip computer performs that function. The point is that, mileage calculations aside, the trip computer mileage should be identical to the start and end mileage you calculated from your odometer and it's not. Odd.
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Old 08-25-2017, 11:23 AM   #7
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Is the on board computer calibrated for the tire size?
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Old 08-25-2017, 11:29 AM   #8
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My 2014 F-150 3.5 Ecoboost computer also overstates mileage by 0.5 to 1 mpg. I never got more than 10 mpg when towing a 25FB, but I also towed through mountain passes on most trips. I also tend to drive a little faster than many.
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Old 08-25-2017, 11:39 AM   #9
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Originally Posted by Dave-n-Janet View Post
Yes, reset at start of trip (hence about 34 mile difference between trip computer and actual fill-up milage.)
. . .
I confess to having missed this difference in actual road miles, as I was focusing on our experience of the computer MPG being consistently 1 MPG higher than the calculated MPG. How many fill-ups were involved, and is it possible that with each fill-up, the computer does some rounding up or down, and that its running total could be off by, say, 1 mile of error for each fill up?

If your discrepancy -- of the actual number of road miles -- continues, I would suggest having the dealer check it out, and perhaps re-flash the system. As asked already, do you have special tires which throw things off? The dealer might be able to program the system for that.

Thanks,

Peter

PS -- You could try to compare the actual road miles for each fill-up with the computer's trip total, then reset the trip miles to zero. In our old '15 Transit, we did this for the first few months to keep track of things.
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Old 08-25-2017, 12:28 PM   #10
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Haven't had truck long enough for further testing. Mostly just use it for towing the AS.

Note to other posters - the mileage difference is because the truck was used to run some errands between the fill-up before trip and actual starting the trip (when trip counter was reset). But note that the 10% difference is almost 10 gal of gas, so don't think 34 miles of errand running could begin to account for it. I get about 20 mpg when not towing.

Actually, just checked my spreadsheet, I've gotten 13.99 mpg over life of the truck (2817 miles) while computer shows 14.6 mpg over life of truck (have never reset the odometer display reading).

It is possible it is miss calibrated due to tire size as the truck has the 20" wheels (from factory). Next time I'm out I'll try and see how odometer lines up with mile markers on freeway.
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Old 08-25-2017, 12:32 PM   #11
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I use to track my MPGs with vehicles and then one day, I had a talk with myself: "So, what are you doing here besides wasting precious time? What changes with doing this? When the vehicle is low on gas, you're still going to fill it up, right?" From that day forth, I threw out the spreadsheet and felt like I had gotten rid of an irksome task.
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Old 08-25-2017, 12:42 PM   #12
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Quote:
Originally Posted by PatLee View Post
I use to track my MPGs with vehicles and then one day, I had a talk with myself: "So, what are you doing here besides wasting precious time? What changes with doing this? When the vehicle is low on gas, you're still going to fill it up, right?" From that day forth, I threw out the spreadsheet and felt like I had gotten rid of an irksome task.
^this! I never bother anymore either. I monitor the onboard computer to watch for any big discrepancies from normal - gives me a clue that I may have some problem going on. I have way too many other fun things to do - like go riding on the motorcycle, watching the sunset with a martini and my sweetie, etc., etc., than fuss with spreadsheets anymore
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Old 08-25-2017, 12:47 PM   #13
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. .
I threw out the spreadsheet . . .
. .
No sheet!

Gave ours up after major surgery two years ago.

Life is short!

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Old 08-25-2017, 12:47 PM   #14
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My 2016 F-150 with a 3.5 Eco Boost is 15% off (high) when not towing and only 1 % to 2% (high) off towing. Best I have gotten is 9.2 mpg (real calculation) vs the 'puter at 9.8 mpg pulling our 2017 30' FC.

We had a 2015 23FB and got 12.6 mpg calculated, the computer always stated high 13's or low 14 mpg.

We have the premium XLT with the larger tires vs the stock 17" rims, I think that is throwing the computer off (some.)

When I complained to Mother Ford they basically said "Oh well."

What really burns me is my neighbors 2013 F-150 with the same engine pulling brand "x big box trailer with two slides" that weighs only 200 pounds empty weight less than my 30' FC and he gets 17 mpg calculated.

I've changed all the fluids to Amsoil synthetic engine, transmission, transfer case and gear oil and it doesn't make a difference in mileage. When those turbos spool up the fuel mileage goes in the toilet.

Hell I only get 16.5 mpg pulling my 1200 pound jon boat, trailer and O/B motor and grandson and yes I do drive like a grandpa.
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