MPG looked good on computer..... - Montana Owners Club

BB_TX · 03-21-2014, 06:09 AM

now I need to check it by odometer and pump readings.

Had to make a quick run to Fredericksburg to pick up an ATV. As I hit the interstate in Dallas I reset the mpg indicator on the info center.

After 170 miles and something over 2 1/2 hours at near steady 70 mph and only one quick rest area stop, no load, three men, and 10-15 mph tail wind, the computer showed 22.7 mpg.
Turned off on state highways, mostly rural, but thru several small towns and traffic lights, and 100 miles later it was 21.6 mpg.

On the way back I had the fairly large ATV in the bed and no wind at all and the same 70 mph. Reset the computer when I hit the interstate and nearing Dallas it was reading 21.9. But then I got the ol' CLEANING EXHAUST FILTER message. Within the next 12-15 miles it dropped to 21.0. But then it climbed back to 21.7 by the time I ran out of interstate. I think the quick rise was due to speed dropping to more of a 60-65 mph range nearing the city.

Those numbers looked great. Now I just need to do some pump and odometer calculations to see how accurate the computer is. My previous truck, also Ford, the computer was consistently 0.4-0.5 mpg higher than pump/odometer calculations. Pretty close. Has anyone with a newer Ford compared the computer to pump/odometer calculations?

Art-n-Marge · 03-21-2014, 06:13 AM

Just completed a 500 mile trip from Temecula in southern California to Sacramento in northern California. Averaged 20.8 at 70 mph, then dropped to about 17.6 when in the two lane roads and high winds, then climbed back up to 19.8 through the San Joaquin Valley (SR 99). Ended at 20.3 by the time we got to the campground in Nicolaus, CA. The best news is I still had 1/4 tank left. I have a 38 gallon stock tank.

It can vary with road types, speeds and winds. When towing I get between 10 and 13 mpgs.

Fire5er · 03-21-2014, 06:36 AM

Sounds right to me. My 2011 6.7 DRW will get 20 to 21 (NOT Towing) straight highway. I get 17 to 18 in town with winter blend diesel, and 18 to 19 with summer blend diesel in town. Now towing...10 to 11 mpg is about it.

**Carl n Susan** · 03-21-2014, 06:46 AM

The 6.7L system is still a tad optimistic (especially when towing), but much closer than my old 6.4L was. Your mileage sounds normal from the lie-o-meter and will be about 0.3 MPG lower when hand calculated.

**DQDick** · 03-21-2014, 02:07 PM

That's what I found with mine also. Once I checked it under different conditions I no longer figure it by hand. It's not different enough to justify the effort.

K0LCB · 03-21-2014, 02:54 PM

I suspect the on board computer measures drive time but not idle time when it computes MPG

hickory · 03-22-2014, 03:52 AM

We just made a 1385 mile trip, towing our 3400RL from WI to Dripping Springs,TX. Onboard read 11.2 upon arrival. It read from 14 to 17 while using it as a daily driver with winter blend in the frigid north country.

steelpony5555 · 03-22-2014, 04:38 AM

Only a 10 mph tailwind?? Here lately it's blow you all over the hwy wind, but it is March in Texas lol lol... It does seem the Fords get a lot better fuel mileage, I can only dream of 21 mpg on my Dodge. I would need that tail wind to get it up to 15 mpg empty and pray there is no wind to get to 11 mpg towing......

twindman · 03-23-2014, 04:52 PM

Per the 'drive time vs idle time' comment. On my 2012 Silverado, if you stop at a light shortly after resetting the mpg, you can see it count down pretty fast. So to me it sounds like it is calculating fuel used per miles driven - whether or not you are moving.

BB_TX · 03-24-2014, 04:31 AM

Quote:

quote:Originally posted by twindman

Per the 'drive time vs idle time' comment. On my 2012 Silverado, if you stop at a light shortly after resetting the mpg, you can see it count down pretty fast. So to me it sounds like it is calculating fuel used per miles driven - whether or not you are moving.

I agree. I have reset mine before and stopped at a light shortly after and the mpg indication began dropping while I was sitting waiting for the light to change. I assume they have some kind of flow measurement compared to the odometer/speedometer to calculate the number.

**Carl n Susan** · 03-24-2014, 08:30 AM

Quote:

quote:Originally posted by BB_TX

...I assume they have some kind of flow measurement compared to the odometer/speedometer to calculate the number...

I remember reading on one of the Ford forums that the on-board computer knows how much fuel is supplied by the HPFP/injectors and obviouly the mileage from the odometer. That is all it needs to calculate mileage. Supposedly what is missing from the calculation is the fuel used in Regeneration of the DPF. That might account for the difference between the "lie-o-meter" and hand calculated mileage numbers.

BB_TX · 03-24-2014, 09:08 AM

Actually during the trip I took last week and watching the avg MPG, when it went into regen the instant MPG indicator dropped significantly and avg MPG displayed slowly dropped over 1/2 mpg over the next few miles before the regen completed and the instant MPG indicator went back up and the avg MPG began to rise again.
Don't know how the extra fuel gets to the SCR but it must be figured into the overall fuel consumption calculation.

twindman · 03-24-2014, 12:01 PM

I wish my regen worked like yours! Mine runs at least 20 minutes and you must be going > 40 MPH. So I figure it knocks about 1 MPG off, maybe 1.5, when driving around town.

Quote:

quote:Originally posted by BB_TX

Actually during the trip I took last week and watching the avg MPG, when it went into regen the instant MPG indicator dropped significantly and avg MPG displayed slowly dropped over 1/2 mpg over the next few miles before the regen completed and the instant MPG indicator went back up and the avg MPG began to rise again.
Don't know how the extra fuel gets to the SCR but it must be figured into the overall fuel consumption calculation.

TLightning · 03-24-2014, 12:17 PM

Quote:

quote:Originally posted by twindman

Per the 'drive time vs idle time' comment. On my 2012 Silverado, if you stop at a light shortly after resetting the mpg, you can see it count down pretty fast. So to me it sounds like it is calculating fuel used per miles driven - whether or not you are moving.

Agree. The computer doesn't know whether or not you are moving...only that the engine is running and burning fuel.

richfaa · 03-24-2014, 03:32 PM

We don't do much driving around town or solo in the 08 F-350. We do not get many regens. It regened twice on our 1200 miles trip to Florida. It is easy to see as the EGT's go up as long as it is in regen. On the rare occasion that we do a MPG calculation we find the difference between the hand calculation and the on board computer is within a couple of tenths.

mtheo · 03-25-2014, 11:05 AM

I like the lie o-meters, have in both of my cars but not in my truck. I trust them but would not put money on it.
Friend of mine alway quotes the milage he gets on a trip. I do the caluclations by hand, he always gets better milage than I do, but on re-filling I almost alway put in less fuel, WHO would guess.

richfaa · 03-28-2014, 05:22 AM

When calculating you must put in the exact same amount of fuel each time when comparing Lie O meter vs hand calculation.
We fill to the brim one more squirt and it would overflow. We can get 4 or 5 gallons in after the auto shutoff. When we do that the numbers are nearly the same. I trust the on board PC for the calculation as it is doing real time fuel use.

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