calculated vs. computer MPG - Please post your results

Miles driven: 362.7
Gallons used: 7.078
Computer Generated MPG: 54.1
Calculated MPG: 51.243

Weather 45-55 degrees roads wet
at times. Typical damp,rain, cloudy
NorthWest Oregon conditions in the winter spring.

With summer, dry roads, temp in the 65-75 degree
range MPG Calculated would be at least 55-57 MPG's.

alfon

 

301.8 miles / indicated 59.2 mpg

Fuel used: 5.228 gallons

Calculated MPG: 57.727

90% highway / temp avg. 55 F/ filled up
at about Sea Level / up to elevation of 1,640 ft / over
Hwy 26 Sunset Hwy to Portland OR /
Filled up again at Sea Level

Roads: Dry

Speed 40-65 MPH

Cargo. two adults

Gas: Costo Brand / Regular / 10% Ethanol / Ethanol
is required all year long in Oregon

 

I filled up my 2004 498 times. The average difference between calculated and MFD was 0.232 mpg with the MFD on the high side. I'd say that's pretty accurate.

My 2011, with 10 fill-ups so far, shows the MFD value high by an average of 2.8 mpg. Every single fill-up has shown an error to the plus side by the MFD. Minimum of 1.3 mpg to a maximum of 4.5 mpg error. This is on every single fill-up. There are no alternations like you would expect if inconsistently filling up the tank.

 

Last 2 times I checked mileage after fillup 3 weeks
part on 5/18/2011 drove 416 miles and it took
7.004 gallons 59.49 miles per gallon I was amazed
As car was only showing 54 Mpg. 3 weeks ago it took just under
7 gallons and averaged 57.6 and the car showed around
52.5 so I thought I had made a mistake on the
Calculations. Anyways I rechecked my numbers saved on my I phone
And they were correct - I am elated

 

Last tank, drove 479 miles, took 9.61 gallons for a 49.8 calculated mpg. The MFD said 53.0 mpg.

 

My last fill up, 434 miles, pump 8.46 gallons for 51.3 mpg. The MFD read 53.4 mpg

 

278.6 miles / 5.058 gal's
MPG Indicated 58.6 MPG
MPG Calculated 55.081 MPG

 

I have noticed that in the last couple of weeks, a big
difference in MPG's.

Roads have been for the most part dry, and temps in the mid 50's, as opposed to temps in the mid 40's with wet roads.

Last fillup, yesterday.

Miles 134.6
Gal's: 2.280
MPG : calculated 59.035
Indicated: 61.8

Gas: reg unleaded, 10% Ethanol, no choice, in Oregon it is
a 10% Ethanol State reqired by law all year long....

If it was not for the Ethanol MPG's would have been over 60 MPG.


alfon

 

Took delivery on my 2011 Prius on April 11. After the first fillup I brought the tires up to 44/42, no other mods. Using 10% ethanol, 87 octane gas. 1,568 miles total. Overall, the indicated mgp is 54.1, the actual measured is 51.7 for a 4.4% difference. Individual data from 4 fillups:

Miles: 371 Indicated: 50.7 mpg Measured: 49.1 mpg Diff: 3.2%
Miles: 341 Indicated: 55.8 mpg Measured: 52.4 mpg Diff: 6.0%
Miles: 431 Indicated: 56.3 mpg Measured: 53.9 mpg Diff: 4.3%
Miles: 425 Indicated: 53.9 mpg Measured: 51.5 mpg Diff: 4.5%

 

Just my opinion but during the summer it appears the mpg guage
is more accurate than in the winter.

Has anyone else have a similar theory?

alfon

 

Miles: 504.3
Gals: 9.595
MPG Guage: 56.1
Calculated: 52.558

10% Ethanol Regular gas

Mixed driving/ two trips up the Sunset Pass Hwy 26
from sea level to 1,640 feet.

al

 

You might want to read this post.

 

Total Miles: 1582

Gal's used: 29.239

Average MPG indicated: 57.96 ( 5 fillups)

Actual MPG calculated: 54.1058

Gas: Regular with 10% Ethanol

alfon

 

Miles: 405.2

Gals's used: 7.657

MPG Computer: 55.3

MPG Calculated: 52.91

Gas used: Costco: Regular Unleaded with 10 Ethanol

Summer is better in a Prius......

alfon

 

Miles: 566.4

Gallons used: 9.167

Calculated mpg: 61.8

HSI mpg: 65.4

HSI/calc MPG: 1.058 = 5.8% discrepancy = enough to be really annoying. Why can't Toyota get this right, when they got so much else about the Prius right??

Gas: Shell regular (probably has some ethanol in it)

 

So 4.5% discrepancy.

 

It does vary sometimes as much as 4 mpg off and as little as 2 mpg


I agree, Toyota could calibrate the MPG guage do read down say 3 mpg that would give a more accurate reading.

My ex-girlfriends 2006 HOnda Civic Hybrid was alway off by about 1-2 mpg in the negative. If the guage read 51 mpg calculated would be 52-53 mpg consistently.

alfon

 

Over 60,000 miles, my Insight-I's computer reads 0.5mpg higher than hand calculated, 84.3 vs 83.8mpg, which is 0.6%. That's about 10x more accurate than the Prius-III. If Honda can do it accurately, why can't Toyota? From what I read here, the Gen II Prii did not have this problem.

 

I'm starting to get convinced that some of my MFD error is caused by leeway that the gas station has in overbilling me.

One gas station gives me around 4% and another gas station consistently gives 6% error. I need more fillups to test this theory, but so far it is a trend.

For instance, pumping at Costco gives less error.

 

Miles: 345.8

Gals: 6.639

MPG Guage: 55.0

Calculated MPG: 52.086

Gasoline: Regular Grade with 10% Ethanol

Driving: normal mix, city and highway, one trip
from sea level to 1642 feet, Hwy 26 Sunset Pass,
and back to sea level, Seaside Oregon. Also
another trip with 5 full size adults in the vehicle, Vehicle Weight
3,950 lbs loaded.

Impressed with the MPG as no other U.S. available car comes
even close.....

Took a look at a Smart Car yesterday, why do they call them smart?
Tiny car with only room for two and a cheeseburger. MPG is only 35-38 mpg and Premium gas is required.

alfon