Average miles per gallon gage

[blizown1]

Is the average miles per gallon gage based off of the total amount of miles on the car or based on current diving conditions or both?

How far back does it take into account?

Can this be reset?

Thanks,

[PhreakdOut]

You reset it from the steering wheel.

I have no knowledge on how it calculates. It seems like the car keeps an average of previous fuel economy so it can zero in on your driving style vs range.

[kingkakyle]

no idea how it calculates but it isn't always accuraet
most of the time its 2+ wat it usually is (i calculate it when i get gas hahaha)
so if its 21 in reality i got 19....SOMETIMES its right.....but 95% of the time it isn't

[Down2TheC]

Pretty sure it just keeps miles and it's view of gallons which is always a bit low (making the mpg optimistic). While the avg of anything is showing, hold the display button until it clears to zero.

Though the range display seems to start at a fixed mpg guess and then runs off the current mpg average once you're further into the tank. (I've done some testing)

[MrMikeL]

There is only 1 way to accurately calculate MPG:

1. Full up your vehicle all the way.
2. Reset your trip odometer to 0.
3. Drive until you have to fill up again.
4. Fill up - record the number of gallons used to fill up the tank.
5. Go to the trip odometer and record the reading.
6. Divide the number of miles traveled by the number of gallons. That is your MPG.

[vuuuuu]

The AVERAGE MPG calculates the MPG using the miles from the point that it is reset, to miles you've gone so far since that point.

So basically, it takes the total average of all of the average miles per gallon points it gets every second or so.

The reason that it is off every time you fill up is because not every fillup will be the same considering the variables: style of driving, temperature, hill grade %, speeds, etc. When you calculate per fill up and you compare to the car's AVG MPG, your comparing it to the overall AVG from when it was last reset.

If you went on a long road trip last month, then that will completely throw off your AVG. Your actual MPG will then be lower than your everyday routine (assuming you live in the city).

[blizown1]

The AVERAGE MPG calculates the MPG using the miles from the point that it is reset, to miles you've gone so far since that point.

So basically, it takes the total average of all of the average miles per gallon points it gets every second or so.

The reason that it is off every time you fill up is because not every fillup will be the same considering the variables: style of driving, temperature, hill grade %, speeds, etc. When you calculate per fill up and you compare to the car's AVG MPG, your comparing it to the overall AVG from when it was last reset.

If you went on a long road trip last month, then that will completely throw off your AVG. Your actual MPG will then be lower than your everyday routine (assuming you live in the city).

Thanks for your reply.

[Down2TheC]

So basically, it takes the total average of all of the average miles per gallon points it gets every second or so.

The reason that it is off every time you fill up is because not every fillup will be the same considering the variables: style of driving, temperature, hill grade %, speeds, etc. When you calculate per fill up and you compare to the car's AVG MPG, your comparing it to the overall AVG from when it was last reset.

If you went on a long road trip last month, then that will completely throw off your AVG. Your actual MPG will then be lower than your everyday routine (assuming you live in the city).

Not to flame, but that's so wrong in so many ways.

-so if you leave it going for two years, it's saving all those reading huh? That would be a great design... It either keeps a running tally of miles and fuel in gallons, or it keeps a running tally of mpg points to calculate. But after a while the second method would be useless since the precision would be limited leading to a situation where new points would be essentially ignored. While the first method you'd only need two integer counters at about 18 bits a piece. (524,287 max)

- The reason it's off every time you fill up, is that it's off all the time. Just by a bit on the hopeful side. Fillups don't matter since the fuel level only effects the RANGE calculation, not MPG. I assume it's keeping track of fuel consumed by how often if fires the injectors. So there will be some play and Toyota wants ppl think their cars are doing great on mileage.

- Not even touching the last one...

[vuuuuu]

Not to flame, but that's so wrong in so many ways.

-so if you leave it going for two years, it's saving all those reading huh? That would be a great design... It either keeps a running tally of miles and fuel in gallons, or it keeps a running tally of mpg points to calculate. But after a while the second method would be useless since the precision would be limited leading to a situation where new points would be essentially ignored. While the first method you'd only need two integer counters at about 18 bits a piece. (524,287 max)

- The reason it's off every time you fill up, is that it's off all the time. Just by a bit on the hopeful side. Fillups don't matter since the fuel level only effects the RANGE calculation, not MPG. I assume it's keeping track of fuel consumed by how often if fires the injectors. So there will be some play and Toyota wants ppl think their cars are doing great on mileage.

- Not even touching the last one...

I'm not offended at all. I'd like to hear other peoples' insights about this.

I'm not saying that it's keeping all of the points as there are few numbers to keep track of. And let me also say that I did not take the thing apart, I'm going with my own theory.

"It either keeps a running tally of miles and fuel in gallons, or it keeps a running tally of mpg points to calculate."

I agree with you that the second method would be out of the question. However, keeping storage of the number of miles and also the current average miles per gallon isn't difficult. If the software keeps a memory location with this value, I don't see how an overflow is possible.

Also, I know we all are making assumptions with how it works, so until we get a Toyota's response, we are all making theories.

As far as what you say about "keeping track of fuel consumed by how often if fires the injectors", I agree with you. I believe that it is keeping track of the amount of gas being consumed whether it's straight at the injectors or some other sensor possibly in the rate of change of the gas tank. Either way, it's keeping track of the gasoline being used and the distance traveled.

Responding to your last comment, have you gone on an 8 hour trip in your car? Your MPG shoots up 3 or 4 mpg (depending on how long you've had your car. Also, have you taken out the battery (or reset your system) and driven completely in the city? Your AVG MPG when you just drive in the city will show a low AVG. This is what I have experienced when testing this.

[vuuuuu]

...So there will be some play and Toyota wants ppl think their cars are doing great on mileage.

You believe that Toyota tricking us into thinking it gets better gas mileage than it actually gets? Not to flame, but that's a bit silly, don't you think?

[MrMikeL]

The on-board computer uses fuzzy math. How does it know exactly how many gallons are used for a fill-up? It doesn't. It can only estimate based on the current level.

Grab your calculators and do it the old fashioned way! Use the on-board computer for amusement.

[jimhild]

In general, this type system gets a computation of the amount of fuel used by the injectors. It then calculates the mileage from the car and computes mileage. Fill -ups don't impact the computer. The average is computed from the last reset, so it is a running average.

Our car is almost dead on with highway driving, it is off about 1 mpg in city/stop and go driving.

In our 1998 Covette the trip computer was almost perfect at all speeds. However, when we changed tires the computer did not know the difference and the trip computer was always off by about 2 mpg after that.

Our city driving mileage is about 24.1 to 25.4 and our freeway mileage at about 70 mph is just over 32 mpg. This is the trip computer, based on the old fashioned methods of fill-up and compute mpg runs 23.6 to 25.3 and about 31.6 on the highway.

[NeFaRiOuS_SLE]

Personally, I think it's just averaging it based on engine RPM, fuel consumption through some sort of flow meter and load levels, plus a few other factors... On Bimmers there's even an MPG gauge that is actively updating as it shifts gears and stuff, so I can safely assume this is based on the same philosophy. This is the thing I was talking about (below the odometer):

[kingkakyle]

Personally, I think it's just averaging it based on engine RPM, fuel consumption through some sort of flow meter and load levels, plus a few other factors... On Bimmers there's even an MPG gauge that is actively updating as it shifts gears and stuff, so I can safely assume this is based on the same philosophy. This is the thing I was talking about (below the odometer):

the gen 2 also has that
is has the avg mpg and also the "instantaneous" mpg as shown in the picture below
so when i floor it, it goes down to about 3-4, cruising at 80 its at 36

[MCOjerry]

That's an old BMW, with an gauge style MPG meter.

Where the hell is that car with -40C outside temp?! That's cold!