Accuracy of dash mpg readout

[Mavster Mechanic]

I run a spreadsheet and record calculated and truck reported mileage. Over 18 fill ups, the truck over reported mpg 11 times with the worst at 5 mpg. The truck under reported mpg 7 times with the worst being 3 mpg. If I average averages it is very close. This is a 25 hybrid AWD. My driving is really all over the place with interstate, city, and highway driving but there is no daily drive so from tank to tank the type of driving can be very different. It seems maybe the truck computer can calculate some types of driving better than others. I'm averaging 40 mpg.

I agree with that.
I drive with with engine off 50% of the time.

The computer may struggle with computing infinity and dividing by zero.
I know I do.

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[Mudduck]

There are differences between same year models based on selected trims. This would lead to some discrepancies, as well as there are some variations between tire manufacturers. When I bought 42" tires for my Jeep, they measured 41.4 but labeled as 42, etc...

 

[MaverickDragon]

With my 25 AWD Hybrid, the dash read mpg and fill up are very close when I go to the first click shut off. Actual mpg figures vary considerably depending on the road and speed of course, but no complaints, as fuel efficiency is outstanding, especially considering it's a truck.

 

[HeyBales]

48 Fillups so far as an avg.
Truck claimed 37.72.
Pump math 37.60.

2 corrections to AFE during that time, awhile back at this point. Should have noted on my sheet when I did it.
I'm good for now.

Can still have fun with the DTE estimates.
Which I can't recall how many miles it keeps in the hopper it's basing the math on.
But I can sure tell when some highway only miles fell out to be replaced with city miles.

 

[MaverickDragon]

But I can sure tell when some highway only miles fell out to be replaced with city miles.

That is true, Atkinson only and the mpg's drop.
I have noticed that not using cruise control helps, as varying the speed (allowing truck to slow down a bit on short up hill travel and speed up on downhill) helps..

 

[Timothyd]

I agree with that.
I drive with with engine off 50% of the time.

The computer may struggle with computing infinity and dividing by zero.
I know I do.

I checked my second tank years ago. It was about 1 mpg generous to the Mav. Haven’t checked it since.

 

[Timothyd]

That is true, Atkinson only and the mpg's drop.
I have noticed that not using cruise control helps, as varying the speed (allowing truck to slow down a bit on short up hill travel and speed up on downhill) helps..

I got very good milage on an up and down highway (rt 44) in Missouri. Also on rt 19.

 

[kevink]

I added a column to my spreadsheet that divides the claimed mileage (which I track) with the calculated MPG.
At any given time, either one can be higher than the other. Especially if I fill up with only a smaller amount, such as 3 or 4 gallons, variations of when the pump turns off can throw off the calculations. Which then throws the next one off the other way.

But, averaging the ratio, it is approximately 5% off. I could get a better average if I factored in the miles on that tank, so give a 5 gallon fillup 1/2 the weight of a 10 gallon fillup, but that would be crazy.

I'm planning to try to see if I can do the recalibration approach.

 

[MaverickDragon]

I got very good milage on an up and down highway (rt 44) in Missouri. Also on it 19.

Mileage on the interstate is good, but it's less than varied speed and terrain travel, which is great.

 

[CaliMav68]

Sounds like things are all over the place. Particularly with the Hybrids. Mine (EB) seems to be pretty spot on. Anecdotally, that is.

I'll be starting a 5k, 2 week road trip next week and will be logging miles and consumption. Pikes Peak is on the list!

 

[Hot Runr Guy]

I'll be starting a 5k, 2 week road trip next week and will be logging miles and consumption. Pikes Peak is on the list!

Don't forget the obligatory pic at the Summit!

HRG

 

[CaliMav68]

It's a well PROVEN FACT the dash readouts run 5% higher than real.

This is true across many makes and models.

Law of Averages means some people will hit spot on some of time.

When betting pink slips, always consider the factory set dash to be 5% high.

This can be user adjusted / corrected on some makes and models.

I manually changed the correction factor in mine to 950/1000. 95%

My dash shows 95% of what the computer thinks my MPG is.

48 MPG computed displays 45.6 MPG.

I agree most vehicles give optimistic results on mpg. The worst was my TDI. 8-10% is just dishonest.

Why would you want to program your truck to be inaccurate the other way? Just wondering.

 

[CaliMav68]

Don't forget the obligatory pic at the Summit!

HRG

Apparently I have to find somebody to take a pic of me in the bed!

 

[Mavster Mechanic]

I agree most vehicles give optimistic results on mpg. The worst was my TDI. 8-10% is just dishonest.

Why would you want to program your truck to be inaccurate the other way? Just wondering.

Not sure I understand what you are asking.

Not sure you understand what I did.

There is a correction factor in your dashboard computer.

Once corrected, the dash is usually within 0.5 MPG of reality. Often 0.2 MPG.

 

[WJOHNM]

I don't care much about gas mileage I avg 30/35,I check it because am a geek, its off about 1/3 mpg. Its my tire pressure that gets me pissed off cant get all tires the same, I know 1or2 pounds don't mean anything, I have one wheel that is always off and it pisses me off, My old friends that haven't checked theirs since the 60s say I should see someone.

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