Question about Fuelly???

Calculated mileage is relatively accurate. The computer in the car is really just a guess based on fuel flow and other factors that add up to a lot of imprecision.

 

The Gen 3 Prius computer seems consistently high, about 5%

 

There's a thread for this:
calculated vs. computer MPG - Please post your results | PriusChat

 

Odd my fuelly is surprisingly higher then my Prius 2014 PIP. I was shocked but Fuelly is telling me I am getting bout 10% more then my PIP. That is why I came here to see if Fuelly was accurate or not. Your seeing it the other way so I am not sure what to believe.

 

To test if Fuelly is correct simply take the # of miles you drove and divide that by the # of gallons you just refueled. That is all Fuelly does.

If you accidentally entered 7.8 gallons instead of 8.7 (or something like that) then Fuelly will be off, but that would be your error. Also, if the pump shut off earlier than normal you could have a bad result because you did not actually fill the tank, but that type of error will resolve itself over the course of a few fill-ups.

 

No one is questioning the accuracy of the calculation of mpg.

They are speculating whether falsely elevated numbers are being entered into the site to boost certain vehicle's mpg numbers. Hence the use of the term "ringers".

SCH-I535

 

I don't see any reference to the term "ringers" in this thread, but I'll believe you since it's better than thinking that the concept of how Fuelly calculates MPG is such a mystifying subject.

 

Oops, sorry, I read another thread and thought your response was in that thread. :embarrassed:

Here is the other thread:

Integrity of Fuelly.com | PriusChat

SCH-I535

 

As others have stated, the Gen III Prius is over reporting approximately 4 to 5% of the true actual MPG.

But what is really important is the gallons you use rather than the MPG.

Example 1: 20 MPG Car travelled 100 miles used 5 gallons of fuel. 50 MPG car travelled 100 miles used two gallons of fuel

Example 2: 20 MPG Car travelled 100 miles used 5 gallons of fuel 60 MPG car travelled 100 miles used 1.67 gallons of fuel.

Example 3: 20 MPG Car travelled 100 miles used 5 gallons of fuel. 75 MPG car travelled 100 miles used 1.33 gallons of fuel.

The less fuel we burn benefits all of us except for big oil. Less oil being converted to gasoline. Less money being spent on fuel. Those are just two of the many benefits.

Remember it is not just the MPG that is important, but also how many gallons you use over time.

Ron (dorunron)

 

The Prius HSI display estimated MPG is only an estimate of your fuel efficiency
The Prius HSI display estimated MPG is consistently optimistic by about 3 mpg
Fuelly calculates your real world MPG when you fill up.

 

My prius display is about 4% higher than actual. The display on cars is based on the fuel injection duty cycle data, so it's not entirely accurate by 4% is pretty good.