calculated vs. computer MPG - Please post your results

It appears that the 2011 model does not change the accuracy significantly - always around 5% discrepancy...although I am flying at almost 7% with my 2010...

 

So I filled it up again here are the results:

179.5 miles
Gal's: 3.925
MPG guage: 55.0
Acutal: 45.732

Total from last tank:
328.4 miles
gal's used: 5.992
MPG acutal: 54.806

Computer MPG average: 58.5

 

Miles: 619.6

Gallons used: 9.501

Calculated mpg: 65.21

HSI mpg: 66.6

HSI/calc MPG: 2.1% discrepancy

Filled to second click, as I did last time.

Discrepancy for the past 3 tanks has dropped from 5.8% to 4.4% to 2.1%. Wonder if that means anything or is simply random scatter.

 

Miles: 233.3

Gal's used: 4.479

MPG Indicated: 55.8

MPG Calculated: 52.087

Reg unleaded with 10% Ethanol

 

Another few fillups on my 2011 pre-quake Prius. Tires at 44/42, no other mods. Using 10% ethanol, 87 octane gas. 2,726 miles total. Overall, the indicated mgp is 54.3, the actual measured is 51.9 for a 4.3% difference. Individual data from 3 more fillups:

Miles: 315 Indicated: 56.0 mpg Measured: 54.1 mpg Diff: 3.5%
Miles: 438 Indicated: 53.3 mpg Measured: 50.6 mpg Diff: 5.1%
Miles: 405 Indicated: 55.2 mpg Measured: 52.8 mpg Diff: 4.4%

 

Liters per 100 kilometers calculated on total fuel consumed and distance travelled since beginning of this year: the in-dash claims are averaging 6.77% optimistic, to date.

 

Miles: 246

Gal's used: 4.066

MPG Indicated: 63.7

MPG Calculated: 60.501

Gas: Reg unleaded (Costco), 10% Ethanol

 

Miles: 598.0

Gallons used: 9.194

Calculated mpg: 65.04

HSI mpg: 68.2

HSI/calc MPG: 4.9% discrepancy

Filled to second click as usual.

 

Miles: 180.3

Gals: 3.093

MPG Indicated: 60.6

MPG Calculated: 58.292

Reg. unleaded with 10 Ethanol / Safeway Brand

alfon

 

Miles: 255.6

gal's: 5.0

Computer MPG: 54.9

Calculated MPG: 51.12

Reg unleaded gas / safeway brand / 10% Ethanol

Mixed driving/ rainy weather / my wife mostly drove
she does not drive for MPG's.

alfon

 

Miles: 617.5

Gallons used: 9.470

Calculated mpg: 65.21

HSI mpg: 68.2

HSI/calc MPG: 4.6% discrepancy

Filled to second click as usual.

 

Thats great mileage. Is that with reg gas with 10% Ethanol?
What's your secret?

Only once in 52,000 miles did I ever get over 60MPG's.

alfon

 

Miles: 397.7

Gal's used: 7.744

MPG Indicated: 54.1

MPG Calculated: 51.355

Reg. Unleaded gas with 10% Ethanol / Costco Brand

My wife drove 90% of the time and she does not drive
for MPG's.

alfon

 

There's an article in the Canadian Press today, saying gasoline purchases are inaccurate by 5 to 7 percent, short changing the customers. I guess I should have payed more attention in algerbra class, but could this be a factor in to the discrepancies between the in-dash display of mileage, vs calculated?

Here's one source:

24 Hours Vancouver e-edition

Not sure if this link is to the specific page: the article is on page 3.

 

I agree, this could actually be the PUMPS. Not the car. We notice it more than other cars because of the extremely high mileahe we are are already getting. People who do the math with 20-30 MPG (traditional cars) won't have such a difference between the screen readout and the calculated I don't think. IDK. I think it could be the pump.

 

Please post original link as I could not manage to find the article. It would be an interesting read.

My last tank showed 4.3L/100km, while measured was 4.48L/100km, or about 4.2%, which is about 30% less than what I usually get (5-7%). The only difference is that I stopped at the first click, while normally I would "push" for at least 2 more...

 

That would be collusion among independent gas stations on a massive scale throughout North America to correlate to the reports from Prius owners scattered all over. Plus, there would have to be collusion among all the individual USA state agencies that regulate trade and measurements and certify gas pumps.

Our Prius has routinely gotten 5% or so less mpg when calculated at fill-up compared to the computer estimate ever since our first fill. On the other hand, our highlander hyrbid actual and computer numbers have been right on the money every time, even though it's only been 3 full tanks so far. I still think it's the Prius.

 

It would be interesting to know what the tolerance is generally for accuracy at the pump. Perhaps there is a common standard that is adopted by most state agencies that gives the gas station owner the benefit of the doubt for about 4 or 5% accuracy?

 

This was in Vancouver's 24 Hour paper. I think their website only shows the latest papers for a few days, that could be why you're having problems with the link. That said:

There are likely still a number of news items on the net relating to this pump inaccuracy. I've read a few more, and now believe the 24 Hour article was inaccurate.

It does seem a little incredible that gas pumps would be an average of 5-7 percent shortchanging. That's an enormous rip-off, if true. From what I've read other places, it looks like the inaccuracies are much less, typically in favour of the station, but not always.

Also, I keep harping on about this, but it is possible to have more accurate in-dash mpg (or liter/100km) display: our last vehicle was an '06 Civic hybrid, which tended to display your mileage slightly conservatively. For example: if it said you were doing 5.0 liters/100km, calculated usually worked out to 4.9.

 

I just got my Prius for about a week. I live in Malaysia.

Today was my first filled.

HSI states 50.3 MPG (4.2 L/100km)
Calculated 48.9 MPG (4.75 L/100km) - difference of about 12%; too far for my liking

I travelled about 508 miles (812.6km) before refilling.

I am thrilled by Prius fuel efficiency. My previous car can get me up to 560km for full tank. Its about 45% further with the new Prius.

I am expecting the fuel economy to improve better once the engine has fully run in. I prefer ECO mode, as it is easier to shift to gliding mode. I don't feel the lag like a number of forumers experienced when I depress the accelerator 3/4 down; its just a matter reorienting the way the accelerator is depressed.