Accuracy of MPG display in Dash

[Tulecreeper]

I only look at mine while coasting down hill or on the off ramp…

It's amazing, isn't it? Sometimes I'll see 99 MPG, but that only lasts for about 6 seconds, then it's back uphill again and down to 12 MPG. But it was nice while it lasted.

 

[yrraljguthrie]

Thanks, my previous vehicle was a Ford F-150 and the dash mpg reading was always about 1.5 high.

 

[yrraljguthrie]

I see several caveats about the effect temperature has on gasoline. Actually, there is very little difference because the air temperature is not important. The temperature of the gasoline in the underground storage tanks does not vary much. Besides being underground they are heavily insulated. This is one reason for not topping off the tank when filling. It's possible to fill the tank and then for expansion of the gasoline to occur and overflow the tank. But this expansion has no effect on the amount of gasoline bought. Doesn't affect calculated mpg. Also, a rise in the temperature of gasoline from 60 to 75 degrees F (15 degrees) will only increase the volume by 1 percent. This is from actual tests and physics. One can disregard outside air temperature affecting the calculation of mpg.

 

[GTyankee]

I have the 32 gallon tank & if i travel where the fuel is cheaper than in California.
I fill my jugs


The above image is of my last Ram, it was a 2009
It also had an 30 gallon Auxiliary tank, i carried around 75 gallons with every thing full

 

[KKBB]

On all the dodges, and now rams that I've had the computer display is high 99% of the time. I have a 2019 2500 with the 6.4 hemi. I just took a small trip...296 miles if I remember correctly. The computer said 18.6 which I was extremely happy with. Once I filled and hand calculated it was 17.1....still not bad at all for the big hemi, but I was disappointed when I had been looking at 18.6 on the screen.

 

[06 Dodge]

After a computer update my old 2006 went from 1.5 mpg off to 4 mpg, now my 2022 so far the read out has been as much as 1 mpg higher then hand calculation to a surprising .25 mpg lower then hand calculation, my self I just assume that I'm getting 1 mpg less then on the fly mpg readout, close enough for government work, I not sure why so many get all worked up and about it, the readout is just a ballpark guess, many factors can & do effect how accrete it is at any time of display...

 

[GTyankee]

I just realized no Hypermilers, have contributed to this subject

 

[Riccochet]

On all of my Ram's the EVIC has always been roughly .5 MPG optimistic versus hand calculation. I've given up caring and only look at the fuel gauge. When it gets below 1/4 I get fuel, when it's above 1/4 I don't get fuel.

If I cared about fuel economy I wouldn't be driving a 3/4 ton gasser.

 

[SIBLY]

I didn't see this posted. It likely has been and I missed it. I've only had my 2023 Bighorn for a couple of weeks and I don't yet have a handle on the accuracy of the fuel reading on the dash compared to real math. Can anyone give me a heads up on how close it is to actual?

Simple.

1. Fill the tank up without over filling it.
2. Reset you trip odometer to zero.
3. Drive it for about 150-200 miles. City driving, highway, or both.
4. Refill the tank without over filling it.
5. Note the total number of gallons needed to refill the tank. EX:15 gallons used
6. Note the total miles driven on the trip odometer. Ex: 200 miles Driven
7. Use this formula: Miles driven / gallons used to refill the tank. Example: 200/15=13.34mpg.
8. Do this five times to get an average which is more accurate of true MPG.

 

[Timsdually]

I trust the computer to monitor how much fuel is being consumed as I drive the truck.
The same as when I pull into the pump, I trust the computer to monitor how much fuel is being pumped into my tank.

 

[Tulecreeper]

I trust the computer to monitor how much fuel is being consumed as I drive the truck.
The same as when I pull into the pump, I trust the computer to monitor how much fuel is being pumped into my tank.

Our gas station in my little burg still has the pumps with handle you have to turn to turn on the pump, and the analog dials that show gallons and price. Old school, baby!

 

[JC4041]

Don't put to much faith in the truck readout.

 

[RASelkirk]

Does this MPG reading somehow reset itself every time you fill up? I've never seen mine do it, nor have I found a way to reset it by hand. Book says "displays average MPG and/or current MPG". My thoughts are average is a cumulative reading over time - like since day #1 when it rolled off the assembly line, and current is instantaneous as in at the moment you look at the reading...

Russ

 

[Dean2]

Does this MPG reading somehow reset itself every time you fill up? I've never seen mine do it, nor have I found a way to reset it by hand. Book says "displays average MPG and/or current MPG". My thoughts are average is a cumulative reading over time - like since day #1 when it rolled off the assembly line, and current is instantaneous as in at the moment you look at the reading...

Russ

If you reset trip A or B it will calculate the average from the reset forward on the trip A or B screen. When you rest the miles to zero you will see the mpg zero out too. You can also reset the running average on the other evic screen.

 

[sam darakjy]

I ignore it. Matter of fact, if I could figure a way to get it off my EVIC screen, I would do that. If I want to know my real MPG, I reset my trip meter to zero when I fill up then just do the math when I fill up again.

Exactly,not sure why people who buy these trucks from any company worries about mpg. I can see maybe a business with a fleet of trucks where it can add up to be a tidy sum for entire year but that is just a tax write off. Any individual owner of a full size truck with a v8 engine just needs to pony up and enjoy their ride.

 

[Tulecreeper]

Exactly,not sure why people who buy these trucks from any company worries about mpg. I can see maybe a business with a fleet of trucks where it can add up to be a tidy sum for entire year but that is just a tax write off. Any individual owner of a full size truck with a v8 engine just needs to pony up and enjoy their ride.

I always ask the same question. No one who buys a 2500/3500, especially to pull an RV, should be giving a rat's a-- about mileage. I know I don't. Gas could go up to $10 a gallon and it wouldn't change my driving habits one bit. I didn't buy the truck I have to save gas. If I was worried about MPG, I would have bought a Prius.

 

[GTyankee]

I sort of think about fuel usage.
I try to plan my route when driving locally

I try my best to make a circle of stops like:
go to the 7/11 for lottery tickets
then go to Albertson's grocery
then stop at the gas station
then the restaurant
Then stop at my P.O. Box
then the donut shop
then the drug store then home

It is almost a Circle, i don't do a criss cross unless i forget something

 

[KyJack]

I didn't see this posted. It likely has been and I missed it. I've only had my 2023 Bighorn for a couple of weeks and I don't yet have a handle on the accuracy of the fuel reading on the dash compared to real math. Can anyone give me a heads up on how close it is to actual?

It's so depressing on my 2020 6.4 I quit tracking it!

 

[Jeff Dougherty]

I didn't see this posted. It likely has been and I missed it. I've only had my 2023 Bighorn for a couple of weeks and I don't yet have a handle on the accuracy of the fuel reading on the dash compared to real math. Can anyone give me a heads up on how close it is to actual?

It seems to me pretty accurate. I use an App called Fuelio. I enter information there each time I fill up and it tells me my average MPG.

 

[Ratman6161]

I always ask the same question. No one who buys a 2500/3500, especially to pull an RV, should be giving a rat's a-- about mileage. I know I don't. Gas could go up to $10 a gallon and it wouldn't change my driving habits one bit. I didn't buy the truck I have to save gas. If I was worried about MPG, I would have bought a P

Exactly,not sure why people who buy these trucks from any company worries about mpg. I can see maybe a business with a fleet of trucks where it can add up to be a tidy sum for entire year but that is just a tax write off. Any individual owner of a full size truck with a v8 engine just needs to pony up and enjoy their ride.

When towing my travel trailer, MPG can be critical bu in an indirect way. What I really care about is range and how far I can go on a tank or how far I can go on the gallons remaining in the tank.
This is really important when heading west and not traveling on the interstate. For example in nowhere KS when I got to my planned stop and found the small town gas station closed. I needed to be able to know what my range remaining was in order to decide if I would carry on to the next town or turn back to a place I passed earlier that I saw was open.

I don't really believe "hand calculated is any more accurate due to too many variables. But since it usually comes in lower, it's a more conservative estimate on how far I can go.