Fuel Economy monitor

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Kinetikad

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Has anyone used the fuel economy monitor . How accurate is it ? Switched from speedometer to fuel economy. Driving a 2014 Ram 1500 hemi quad cab.
 

RamNSubie

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I use mine, it seems pretty accurate but I have yet to calculate my mileage by hand.
 

darthdzl

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The consensus among the figures I've seen (including mine) says it reads 1.5-2mpg too high. That's not just a RAM thing, though...my VW did the same thing, more or less.
 

EagleChief

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I haven't calculated mine by hand yet, either. But, it seems to be pretty accurate. Between my wife driving it during the week (lead foot), and me driving it on the weekends, I show between 16.8 - 17.2 on the monitor. I can usually get better mileage than she does.
 

cgeorgemo

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Mine reads about 2 MPH high on highway trips and 1 MPH high in the city.
 

dhay13

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mine is pretty accurate. usually slightly higher than actual. i check mine every fill up (twice a week). last week it read 19.4 and i actually got 19.8. i drive 100 miles a day and its about 90% highway. but i don't think it has ever been more than about .5 off
 

RamNSubie

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I'm curious how you guys are estimating accuracy without an actual figure to work from.

I haven't put numbers into a calculator and scrutinized it. It's more of, I put 20 gallons in, the computer says I got 17 mpg, I did over 300 miles, its fairly close. I'm an operational engineer by trade, quick close figures are easy for me.

For those that are saying they get larger discrepancies I recommend a procedure to find true accuracy.

Use the same pump 4 times in a row, only fill until it shuts off automatically.

This will negate any meter/pump differences. All meters have a tolerance for being slightly off from exact. Also each pump might shut of a little different so stopping when the pump stops is another controllable data point.

Basically, use the scientific method for conducting experiments and results will be fairly accurate.
 

darthdzl

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For those that are saying they get larger discrepancies I recommend a procedure to find true accuracy.
How about 13k miles using a smattering of different pumps all around the Phoenix area, with every tank falling into the same range (EVIC reading 1.5-2.3MPG too high), as well as the overall average being off within that same range?

Is that enough? :)

I keep track of every tankful in a spreadsheet, with both one-tank and cumulative averages, as well as a bunch of other stuff (cents per mile, miles per day, etc). And I always make a mental note of what the EVIC said before I reset it. I don't preserve those numbers, as I'm only interested in the actual hand-measured ones, but it's never been less than 1.5MPG high or more than 2.3MPG high. Oh, and I always fill only till the auto-shutoff.

I'm not doubting your math skills or observational skills. Just saying you can't really measure accuracy with an actual measurement. You can suspect it's close, or estimate that it's about right, but "about right" could be different things to different people.
 
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Kinetikad

Kinetikad

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How about the " Range " readout ? Sometimes I'm always from a station and am curious if that's a good reference as to when I'm in danger of running out of gas . I never go below a 1/4 of a tank , but was curious .
 

RamNSubie

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I'm not doubting your math skills or observational skills. Just saying you can't really measure accuracy with an actual measurement. You can suspect it's close, or estimate that it's about right, but "about right" could be different things to different people.

About right on the EVIC measure for me is within 1 mpg. If I put 20 gallons in and did about 330 miles +/- 5 miles then my mileage would be 16.25-16.75 mpg. Keep in mind that 1 mpg difference in reading if getting 17 mpg is only a 6% error. Gas pumps can have a .3% error, pretty small really. As I am unsure of how the monitoring system is actually designed it is hard to say what the actual tolerances are on each item. From learning/working with instrumentation I can say making it to a 6% error is very possible especially when it is for something non-critical such as an economy meter.

I am currently at work, burning 600 to 2800 gallons of diesel a day, but will go through my own process finally.
 

dhay13

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2013 Ram Express Hemi (Ram 1500) | Fuelly

i have tracked mine since the day i bought it. and also keep a spreadsheet. i don't 'compare' them to my readout but i know it is pretty close. right now it reads 19.2. i'm willing to bet when i fill it up sunday it is very close to that. probably about 19.1 or so. i know this because of the daily commute and how my mileage has been but i will try to remember to check it and post here
 

RamNSubie

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I did a bit of research. From what I found most manufacturers use data from the injector commands. The computer knows how much fuel it is saying to inject, it also knows how often fuel is injected. You have a number of tolerances that can contribute. Naming the ones I can think of: engine speed(and the method for obtaining it), injectors, density of fuel(gasoline is very temperature sensitive), tire size, odometer, fuel pump meter. That is at least 6 points that have acceptable tolerances.
 

darthdzl

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About right on the EVIC measure for me is within 1 mpg. If I put 20 gallons in and did about 330 miles +/- 5 miles then my mileage would be 16.25-16.75 mpg. Keep in mind that 1 mpg difference in reading if getting 17 mpg is only a 6% error. Gas pumps can have a .3% error, pretty small really. As I am unsure of how the monitoring system is actually designed it is hard to say what the actual tolerances are on each item. From learning/working with instrumentation I can say making it to a 6% error is very possible especially when it is for something non-critical such as an economy meter.

I am currently at work, burning 600 to 2800 gallons of diesel a day, but will go through my own process finally.
Fair enough. But I think the OP was looking for an actual number, even if approximate, of how far the EVIC tends to be off. It's kinda hard to get that without comparing it to actual measurements.

However, your point is taken.
 

dhay13

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well filled up today. 394.6 miles and took 20.177 gallons to fill it...19.6 MPG. my overhead read 19.7. i reset it at each fill-up before i pull away from the pump. maybe mine is more accurate because 95% of my driving is highway with a steady throttle. not much on and off of the gas?
 

RamNSubie

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well filled up today. 394.6 miles and took 20.177 gallons to fill it...19.6 MPG. my overhead read 19.7. i reset it at each fill-up before i pull away from the pump. maybe mine is more accurate because 95% of my driving is highway with a steady throttle. not much on and off of the gas?

It is very possible that could be a factor. Like I mentioned, every single item on a vehicle has a tolerance. The parts that deal with fuel economy monitoring on your truck could just end up having very little deviation in the end compared to others.
 

xrsman

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Has anyone used the fuel economy monitor . How accurate is it ? Switched from speedometer to fuel economy. Driving a 2014 Ram 1500 hemi quad cab.
Normal driving around with in city short trips mixed with highway mine tends to be 1 L/100 kms off. However when I only drive highway and longer trips it's always very close! Maybe within .1- .3 of what the truck says.
How about the " Range " readout ? Sometimes I'm always from a station and am curious if that's a good reference as to when I'm in danger of running out of gas . I never go below a 1/4 of a tank , but was curious .
Driving around normally I find that the range makes you think you have a bit less fuel than you do (which is good). However I went down to Ohio to pick a trailer up (120 km/h the whole trip) and wanted to see if I could do it on 1 tank of fuel. (750 kms). When I was about 40 Mins away my range started dropping fast! Like 5 kms per minute. Usually it doesn't do this so it was a mad rush to find a gas station! I filled up and had I believe 15 liters to spare so I probably could have made it lol.

Bottom line, you usually have more range than it says you do. In my case anyway
 

EagleChief

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I'm curious how you guys are estimating accuracy without an actual figure to work from.

Mine is basically an assumption... and, yes, I know what that means. Judging by my other vehicles and the mileage between fill-ups, I'm guessing my EVIC mpg's are not that far off. Who knows... maybe I'm only getting 15-16 mpgs, when it reads 17.5.
 
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