calculated vs. computer MPG - Please post your results

I've saved data on all of my tank fills for my 2010 Prius purchased in August 2009. The attached jpg shows seasonal variation in MPG, and also compares the car computer estimate to the actual calculated MPG. The car computer is almost always 5% high (average 5.2%), within my actual mileage range (low of 46.5, high of 58.4).

 

So we are talking about 4% offset, is this seen on many prius after all those posts? Sorry if I didn't read all the posts.

 

Nice post. I love data.

 

Thanks. Old bankers always like to keep numbers.

 

Here is the data from my first 7 tanks. It looks like a pretty predictable relationship between calculated (actual) and indicated (computer).

 

It seems that in summer my MPG gauge was off by about 2.57 mpg over read. In winter it seem to run 3-3.5 MPG
over read. I believe its due to summer weather being warmer and fuel expanding in the tank due to cold temp's from ground gasoline tank to warm ambient air in summer.

 

Update.

As of 4/4/2013, total miles logged = 69071.9 total gasoline consumed = 1147.8 gallons.

Calculated = 60.2 mpg
Displayed = 63.6 mpg
Difference = 5.7%

 

Did you recently buy new tires?

 

You really should use percentage variation, not just mpg, because 2.57 mpg vs 3-3.5 mpg doesn't really tell anyone much. For instance my last tank was 58.6mpg displayed vs 55.6 mpg calculated for a difference of 5.4%.

 

800 miles without resetting.
Indicated MPG 53.8
Calculated MPG 51.3
Looks like a little over 5% over read.
96,000 miles on our Prius now....

 

My first calculated tank gave me 49.7 MPG with the readout displaying 53.2. My car had about 1,500 miles on it, so it's pretty fresh still (though reading threads it seems MPG doesn't really improve during break-in periods).

 

Over 100 logged Fillups and the calculated is always about 5% lower than the displayed.

 

Has anyone compared (with detail) regular unleaded gasoline against ethanol based (10%) fuel? I see a 3-8% error consistently on a couple of Pri, and, short of Toyota marketing interfering with engineering...

 

My new V5 shows the same percentage difference between displayed and calculated. Recent tank showed 48.5 mpg but actual was 45.7 mpg. My previous '10 Prius IV showed same difference - 5-6% off.

 

1st fill up;

54.0 Displayed
51.4 Hand Calculated.

Travis

 

Up to about 1200 miles total and last fill up showed 54.9 mpg over 450 miles or so and the actual was 53.4. So not to different.


iPad ? HD

 

First tank calculated with Fuelly: 50.1 mpg and my car shows 4.4 l/100 km (53.4 mpg).

Does anyone here know what is the reported l/100 km when the displays switches ex: from 4.4 to 4.5 l/100 km ? Is it 4.499 or 4.4499 ?

 

I tracked the first two years of my 4-year-old 2010 and have recently started tracking again. The difference between displayed mpg and calculated mpg has generally between in the 3-5% range, although it's occasionally been higher.

 

The indicated MPG error on mine varies a lot compared to the actual MPG, but that's likely due to variances in fill up, even though I try to be consistent. The error averages out to be 6.37% over 97 fill-ups.

 

I asked Toyota and they answered me this:

So I think it means the answer to my question is 4.449, it's in the middle.