calculated vs. computer MPG - Please post your results

The California requirement is that the pump be accurate to within 1/2% when filling their standard 5 gallon test container. That 6 cubic inches out of 1155 cubic inches. Something like 95% of pumps in Califonia meet that standard and some of those that don't pump more than the pump says.

http://www.co.shasta.ca.us/grand_jury/0809_reports/SC_weights_measures.sflb.ashx

That's not to say you aren't getting an inaccurate pump, but the odds are there is another explanation. Perhaps fuel formulation.

 

Fuel formulation that affects Gen-III Prii and not Gen-II Prii or Honda Insight-I's????

 

Of course not.

 

The Smart car was made for the European market, for "cramped" EU cities. Not for the US market with it wide roads and easy parking. The only reason it is sold now in the US, is because there is raised interest in fuel efficient cars and Mercedes has nothing better to offer...and probably also because they thought that the Smart would be a "cool" car, in the same way the "Mini" has become (or not?) in the US.

The only Smart that really consumes less is the Diesel version, which likely is not sold in the US at all.

For me the Smart is a very expensive car (for what it offers) and is only justified if you live in a town with very narrow streets and/or big parking problems (it is a *huge* success in Rome). Otherwise, if you need to do anything more than carrying another person, it is a waste of money.

 

It's possible that the Prius-III has a different method of measuring fuel usage from what was used previously, and that this method tends to read high.

I hoped that Toyota might have a way to recalibrate the readings, so I phoned Toyota Customer Service. Who said they weren't aware of any procedure for doing that, but that I should take it to a dealer. Who would do what, exactly?? Seems like a waste of time unless the system can be recalibrated/reprogrammed, which apparently it can't.

I'll just have to work on doing a 6% correction in my head. It's simply half of 10%, plus 1%. And both 10% and 1% are easy to figure. Calisthenics for the brain.

 

+1
In Turin one often sees Smarts parked perpendicular to the curb. They're about as long as a regular car is wide. Very amusing to see, very convenient for the driver, and probably illegal.

 

I met with my brother over the weekend and he owns a Yaris I believe from 2007.

He told me that the MFD is about 3-4% off for the fuel consumption and then we measured, using my portable navi, that the speedometer, which resulted 5-6% off.

Compared to 6-7% and 9-10%, respectively, of the more expensive and newer Prius Gen 3 from 2009 I own, it is a shame from Toyota to sell a car so imprecise.

I am too afraid now to check how accurate is the km counter... I don't want to have bad surprises on that as well.

 

I've had my Gen III for nearly 2 years now. It has consistently hovered around 2.1 mpg generous, when compared to calculated. It is also 2 mph generous which I guess is normal for most cars. I've checked it out via calculator and two gps units.

 

Measure the odometer separately from speedometer. At least in the U.S. market, they have different errors. Speedometers must read high for legal and industry standard reasons, and I've heard of even larger errors in certain European markets. But odometers cannot have similar errors without inviting class action lawsuits for warranty fraud.

Last fall, my Prius's odometer was reading 0.2% low, not high. The manufacturers of both my previous cars have settled lawsuits by extending their warranty mileage 2%, though both of mine were within 0.5%.

 

Miles: 612.6

Gallons used: 9.688

Calculated mpg: 63.23

HSI mpg: 66.0

HSI/calc MPG: 4.4% discrepancy

Filled to second click, as I did last time.

 

I'll just add more detail for whoever wants to take up the challenge.

At two years, my display error has increased to 6.6% over the car's life, or 7.5% over the past year.

At the most recent refill, N=72, Odometer = 28522, total pumped fuel = 539.31 gallons, HSI-imputed fuel = 505.99 gallons.

 

My reading was 56.8, my calculated was 54.74 i think 2 mpg isn't bad.

Poor computer was probably confused cause my wife drove over 100 miles and she drives way different than I... It's gas / brake... no glide...

 

Has this been improved / corrected in the '11 model?

 

Miles: 492.3

Gal's: 9.041

MPG Guage: 57.4

Calculated MPG: 54.451

70% hwy / 30% city approx.

Fuel: Costco Regular unleaded with 10% Ethanol, "required all year
long in Oregon".

alfon

 

miles: 148.9

gal's used: 2.067

MPG Guage: 62.0

MPG Calculated: 72.036

Reg. Unleaded with 10 Ethanol

Hwy 90% 10% City

Note:

When I filled last time at slow speed when the pump stops thats it...

So after 148.9 miles the guage was still reading full. Normally it would drop down to 2 -3 pips from full.

So I went to the same gas station I had previously filled up, a different pump but the same type and filled at slow speed, first click that was it....

So I am baffled why. I could see if it took 2.5 gal's but a little over 2 gal's. I have never had this happened. Also the gas guage still read full.

alfon

 

I have a 2011 Prius III. Here are my results in a 2264 mile sample size.

Computer MPG
48.66
Calculated MPG
46.98

3.42% difference

 

After four tankfuls and 1,800 miles on my 2011 Prius, my stats are as follows:

Last tankful:
502 miles
55.0 computer MPG
52.6 calculated MPG
4.63% discrepancy

Overall:
1,862 miles
53.5 computer MPG
51.0 calculated MPG
4.92% discrepancy

My first tank was filled with 10% ethanol and had the largest discrepancy (6.07%); but that could be because it was the first tank. All other fill-ups have been with 0% ethanol.

 

No. I have 16 fill-ups now in my 2011. I am averaging 2.46 mpg higher on the display than calculated.