avg mpg accurate, single drives not so much

welcome!

the average mpg on the dash is 76, and computed at the pump is also 76?

 

Take a few minutes to dive deep into your OM. It actually explains why you are seeing what you’re seeing. Also, get ready for some REALLY IGNORANT responses! . I’ve got a’22 also, and see very similar averages. Again, the manual actually addresses it and it actually makes sense.
Some here believe (and remember, beliefs are seldom based on real world facts anymore) that Toyota has something to gain by convincing you that you are getting better mpg than you are (apparently believing, also that Toyota thinks none of us can do basic math), so get ready for the conspiracy advocates to chime in on this: trust your math and your manual.

 

You are using the wrong math to compute combined trip average, because the denominators don't match. Try this instead:

Downhill fuel used: 1 / 170 gallons per mile = 0.005882 gal/mile
Uphill fuel used: 1 / 55 gallons per mile = 0.018182 gal/mile
Round trip sum = 0.005882 + 0.018182 = 0.024064 gallons per 2 miles round trip
Round trip MPG = 2 miles / 0.024064 gallons = 83.1 MPG.

83 is much closer to your displayed 76, than was the method you used. And considering that you gave round numbers, that is close enough.

Most countries express fuel economy as liters per 100 kilometers. If we used either that, or an English equivalent such as gallons per 100 miles, then we could do a simple average and get the right answer.

 

The other thing I recall from High School mathematics - you can't average averages (unless - as mentioned above, the denominators are identical, or at least similar).

 

Oh geez, I've got to rise to that:

 

My own diff-eq and complex variables and linear algebra are also extremely rusty by now.

 

ditto . I did schooling BC (before calculators). Even slide-rules were ... I think steam driven.

But - since school - I haven't knowingly used calculus, differential equations - or most of the trigonometry I learned. BUT - the learned concepts are undoubtedly in use by my brain still, 50 years later.

 

LOL I wondered how long you could let me get by with that!

 

It's funny, looking back on the stuff we were taught:

Penmanship
Arithmetic
Geography
History (ancient history)

Today's grade school curriculum pale. Maybe for the best.

 

Sometimes I feel like I came from there - the way things are progressing.

All my cars in the past - you press the button to open the glovebox.

A friend was telling me that he had to ask how to on his new car:

Answer: To open the glove box:
1) tap the car icon (Controls) at the corner of the screen
2) tap the Glove box button on the screen.
3) The glove box opens.
4) you roll your eyes just wondering.

 

Soon, you will have to buy a subscription to use your glovebox. Thanks BMW!

 

Yeah, lots of people have trouble with basic arithmetic. Gallons per mile would be less confusing than miles per gallon. Average mpg is the inverse of the average of the inverses. Thus
(1/170+1/55)gal./mile/2 = (1/83.1)gal./mile .

 

^^^ You just made it more confusing!

 

While most say their dash MPG is under what they actually get, mine is consistently 2-3 mpg less. (Says 59-60 but when I fill it up it's 57-58) I suspect it due to being at 7,000 feet above sea level and our regular gas is 85 octane.)

Recently, however, I replaced my engine air filter and inflated the tires to 37 mpg (recent cold caused TPMS light to come on and few were low.) Now, the car is reporting 64 mpg so it'll be interesting to see if I actually get 61-62 now.

 

At least for me dash-displayed mpg is invariably higher than calculated, by an average ~7.5%. I think that’s the consensus here too?

 

They do? That is the opposite of what I've been reading. Like yours, my dashboard MPG is a bit higher than reality. The vast majority of reports here, at least on my vehicle generation, are similar.

 

My dash reports better mpg most of the time. Sometimes it is correct.

10k @ 52.9 mpg