calculated vs. computer MPG - Please post your results

Where to you find the displayed mpg on a 2012 Prius III? It used to be along side of the trip odo

 

op2: "What in the same" ..... Do you mean "What in the name" ???:violin:

:deadhorse: .... It's DEAD ..... They are VULTURES !!!

..... KINKY is GOOD ..... n'est-ce pas ???

:cheer2:

 

Filled up three times did not reset:

Miles: 1,385.7

Gal's: 26.614

Average indicated speed: 37 mph

MPG Indicated: 54.9

MPG Calculated: 52.067

Difference 2.833 mpg

Tires: Michelin Energy Saver/ 195.65.15/ 44 psi in all four

Gas: Unleaded Regular with 10% Ethanol

Temps: 40 - 65 degrees/ roads wet with rain
at times. Average temp 50 degrees.

 

Only 3.5% CONS gage error -

27 MPH avg
57.5 MPG indicated
55.5 MPG actual
524.2 trip miles
9.437 gallons refill 87 pump octane

Mostly dry
70% hwy miles at low to high 60's MPH

30% city with some horrible traffic jams in there
60s to 70s F weather
tires stock Goodyear Assurance? (38/36 psi front /rear)
single occupant driving
No cargo

 

Those 3 heads are "beating a dead horse", which is a phrase that means the issue has been concluded but some people continue to debate the issue. You can beat on a dead horse, but it won't move, it is still dead, no matter how much you beat on it.

 

Avg speed 26 mph
Indicated mpg = 58.2
Calculated mpg = 56.2

error = 3.4%

Is that normal for a 2012 Prius?

 

I have had anything from a -3.8 to -7.2% difference.

My last tank:

Average speed 24mph

Indicated mpg = 57.2

Calculated mpg = 53.1

Error = -7.2%

 

If you wish to be 100% consistent in actual and
computer generated mpg, fill up the tank to the
top of the neck were you can see standing fuel.

Drive until you are almost empty. Fill up again
if possible same pump and fill to the same
level as the first time.

Result will be 100 % accurate and you can see the
true difference in calculated and computer generated
mpg.

This is how Wayne Gerdes from Cleanmpg.com does his test....

 

I drive a mix. of city and free-way in Tampa Bay area in Florida where gas is now 3.48 a Gal and get about 46-48 from calc. fill-ups and 50-52 on dash board read- out. Still getting used to coasting and breaking. Hope this helps.

 

About average from most on Fuelly at least for mpg's. As for the cost of gas, lucky you! Our gas prices are all over the map in the Northern Virginia area; best is just over $3.71 or so. Closer to $3.85 if you are willing to drive an extra few miles from the $3.90 that many are still showing.

 

First Chip c'mon down to Richmond --- $3.56 yesterday

Second - yesterday I got 50.9 calc vs. 54.0 displayed -- variance 6%.

 

just filled up with "cheap" fuel in suburb of Chicago (3.93).

Actual MPG 55.78 - Display - 58.9

 

over 35 fill ups logged 16,000 miles I calculate that my prius reports an MPG 5.87% higher than what I actually calculate out. I image that could just be for variance in how much fuel actually goes back into the tank and when the pump decides to shut off. I always stop at the first click when filling.

 

For a 2011 model 5 .Getting 39 mpg actual while computer states 43 mpg. In South Florida using AC mostly and city driving. Price is at $3.49.

 

Just an update, all my tanks read 2.2 mpg higher on the HSI display, than I get in actual calculations after filling up.

 

IIRC filling vehicles to the brim of the tank neck allows raw fuel to make it's way into the evaporation canister damaging it beyond use. As well, on a hot day if there is no room in the tank or neck for vapor expansion you have a pressurized container under your vehicle which could potentially be a dangerous situation in itself. Hose damage may also result from lack of room for expansion.

 

did not reset A trip after a few fillups here are the results:

Miles: 1261.1
Indicated: 56.0 mpg
Calculated: 53.870
Average speed: 34 mph
gal's used: 23.41
Gas: 10% Ethanol Regular grade gasoline

 

One fillup in the above composite: camping trip vehicle
loaded with three people, 100 lb black lab, and heavy gear:

Miles: 269.7
Indicated mpg: 61.8
Calculated: 60.1
Avg. speed: 36 mph
Gal's used: 4.483
Reg gas 10% Ethanol

 

I avoid this tactic for a couple of reasons:

1. I don't want an accidental spill
2. If the carbon trap in inundated with fuel it cannot function to reduce pollution
3. Repeat wetting of the carbon trap may damage it
4. Toyota says not to

As for fuel economy accuracy, I simply calculate after a couple thousand miles of driving. The 'tank-full' to 'tank-full' error is reasonably constant and has an upper bound, so I (as it were) enlarge the tank to decrease the percentage error. Wayne has to give the car back in a day or two; we owners can have the accuracy without the problems.

 

I've followed the discussion for a few months now and finally have a full month of data for my 2012 model 2. My variations between the display has been higher than my calculator from 1.5% to 7.5%, on average, close to 5%. However, when backing into the number of miles "still in the tank", it is always off about two gallons X the calculated average MPG. That is very conservative but I would rather have accuracy. Since I was intentionally trying to gather the data, I always used 10% ethanol and was very careful to complete my fill ups the same way. Can anyone tell me if this is a Toyota software bug or intentional. I attached my spread sheet.