Computer Mileage Question

alaskaman

alaskaman

Senior Member
so I am driving to work this morning tank is about 3/4 full and the computer says 16.5 mpg....so I say to myself...."never been that low"...so I hit reset and it goes to 0.0 and then bounces every 20 seconds or so until after about 10 minutes settles in at 19.2 and goes up from there to about 20.0 after steady freeway for about 60 miles........can some one tell me what this all means?

Thanks.....
 
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Not much, the computer is always off. Usually by about 10%. Just do it manually if you want your real average.
 
yah.....wonder how it samples for getting the gas mileage..........and why it would be consistently off......should be as easy then to be consistently on one would surmise.
 
It's an inaccurate measure of your mpg for the time from where you hit the reset button and when you read the gauge. For example, if you hit the reset and then sit at a red light for 5minutes, your reading will be much lower than if you hit reset while driving lightly at 55mph on the highway.

FWIW, I hit the reset every time I fill up. Knowing that its probably an optimistic reading of my mileage.
 
i pressed reset before i did a little trip the other day. then i proceed to sit stopped on the freeway for 2.5 (traveled all of 9 miles) and it read like 8mpg once that was over. I did a 250 trip and when i was done the computer said 20.6, but i actually calculated it and it was about 18.3.
 
as far as I understand it's just a calculation by the computer based upon a throttle position sensor. You reset it at each tank fill up and it will give you an approx avg for that tank. You hit reset on the highway and it will give you an approx that you are getting right then and there but you lost the whole tank avg. I haven't compared the computer estimated avg MPG to the math way yet but I'll try to remember next time.
 
It's calculating your average, not instant. Apparently you had been driving the 4R a little hard, and got 16mpg. Then after u reset it, every second was a big increase in data. Thus, it will jump around until there the ratio of new data to previous data is high enough for it not to have a big immediate impact.

For a comparison, remember back to your GPA.
 
I believe I read here in the forum that it monitors the activity of one injector, and that the reading is an average mpg.
 
josh220 said:
Not much, the computer is always off. Usually by about 10%. Just do it manually if you want your real average.
Click to expand...

When not towing the dash display in my 4Runner runs 13-15% higher than actual, calculated MPG.
When towing the dash display runs about 9% higher.

It is kind of sad that Toyota cannot get this correct.
If other manufacturers can do it why can't Toyota?
Oh well, maybe the next generation of 4Runner will get this right.
 
My computer is always damn close to my manual calculations . Never had the problems with it other have had being use less of way off.
 
Falls said:
My computer is always damn close to my manual calculations . Never had the problems with it other have had being use less of way off.
Click to expand...

I think it mostly has to do with the type of driving you do, and how hard your drive. If you are always pushing the throttle hard, your reading will go down pretty fast. But if you drive it gently, and coast as much as possible, then it tricks it into reading higher.
 
josh220 said:
I think it mostly has to do with the type of driving you do, and how hard your drive. If you are always pushing the throttle hard, your reading will go down pretty fast. But if you drive it gently, and coast as much as possible, then it tricks it into reading higher.
Click to expand...

I agree with that. Keep in mind that the computer doesn't take into account things such as startup fuel
 
Falls said:
My computer is always damn close to my manual calculations . Never had the problems with it other have had being use less of way off.
Click to expand...

Do you reset your average MPH and average MPG after each fill up? Speaking of fill ups do you always fill the tank entirely every time you fill up?

Just wondering if you are doing something different when it comes to your MPG display being much more accurate than the rest of us.
 
There has been several discussions of this over the years. Odometer under-reports 3% and computer over-reports 7%+ . Been checked numerous times against GPS & freeway markers.

(and yes, I run the factory tire size)

Basically at non-towing highway speeds and it shows 20 mpg, subtract about 2 mpg from it to get close to actual.

When towing, and you're down around 10 mpg, subtract 1 mpg .
 
TeryT said:
There has been several discussions of this over the years. Odometer under-reports 3% and computer over-reports 7%+ . Been checked numerous times against GPS & freeway markers.

(and yes, I run the factory tire size)

Basically at non-towing highway speeds and it shows 20 mpg, subtract about 2 mpg from it to get close to actual.

When towing, and you're down around 10 mpg, subtract 1 mpg .
Click to expand...

Never found anything of the sort on mine .


Yes I always fill up and am an aggressive driver. I do check my milage on occasion now to make sure everything is in check , I do not reset the comp , matter of fact I have the display turned off , but when I do its pretty much right on.

I did a little test once where I set the cruse control on a hiway at 55 , then reset the comp. for the avr. speed and it came out right on.
 
.....on the highway my comp will read about 19.5 to 21.0. when I fill up when the light comes on it take 20 gallons and I get about 350 to 400 miles on that 20 gallons.
 
alaskaman said:
.....on the highway my comp will read about 19.5 to 21.0. when I fill up when the light comes on it take 20 gallons and I get about 350 to 400 miles on that 20 gallons.
Click to expand...

I get about 250 miles for the "trip" reading, so I think I need to try another gas station because i'm averaging 12mpg, had 13.x once. That's low even for a 4WD V8.
 
Falls said:
Never found anything of the sort on mine .


Yes I always fill up and am an aggressive driver. I do check my milage on occasion now to make sure everything is in check , I do not reset the comp , matter of fact I have the display turned off , but when I do its pretty much right on.

I did a little test once where I set the cruse control on a hiway at 55 , then reset the comp. for the avr. speed and it came out right on.
Click to expand...
Have you cheked it with a GPS? Reset everything (odometer & GPS) to zero when you cross a mileage marker. Go for 10 miles, then see. (also need to check that the highway markers are accurate)
 
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