calculated vs. computer MPG - Please post your results

Thanks, this current tank is not going to be that good. I sat with AC for a while twice hooking up my new SGII and my car has been acting funny.
I drove to dinner today 2-3 miles one way. The whole way there my ICE wouldn't turn off which is unusual. Every stop light the RPM was 1000-1100. Wouldn't go EV the whole way there. The way back it went into EV finally at the end.
Usually it never takes that long and goes to EV within a minute or two.
At 150 miles i'm down to 55.5 mpg from 58-58.5 reading a day and a half ago. I'm picking up people at the airport tomorrow so it should go lower since I got to crank up the AC @ max and I won't be able to hypermile as much.

 

" I have noticed that when it is really hot outside (100F+) the car won't let me activate EV Mode. This happens....."

This must be it. Usually it does well but once in a while I have trouble going to EV.
When this happened today my SOC was 66.6%. After a mile of driving it dropped considerably in the low 50s% and the ICE remained on the whole way.

 

The pump might not have shut off until an additional 0.1 gallons were added. That would take your calculated up from 62.7 mpg to 63.3 mpg (and a 4.9% error). I suspect you'll see a little pop in your next tank, assuming all the other tanks were normal and assuming there was nothing wrong with the displayed fuel delivery numbers (ie the pump didn't cheat you).

 

Ya know..........

What might be interesting is to turn off the HSI altogether (such that you can't see the bars) and "just drive the car normally", otherwise you may be tempted to peek......

Get in, change the display to non HSI, focus on the road and your mirrors and off you go, A/C at a comfortable setting (78? 75? 72?) while listening to "Pretty Little Hate Machine".....good times!

 

8,617.5 miles / indicated mpg's - 56.1 / calculated 53.54 / avg. indicated mph 40 /
gals' used: 160.955 / diff. 2.56 mpg
Gas is reg with 10% Ethanol
Tires for the last 500 miles / Bridgestone ep422 Ecopia (44 psi in all four tires) / 195x65x15 (before that Michelin Energy Saver AS) / with 44 psi in all four tires.

 

I can save most people a lot of time! I tracked a 2011 through 30,000 miles and the vehicle computer MPG averaged 5% MORE than actual hand calculations. This percentage varied between 4% and 5%, but was always overstated. I found a website once that said that most if not all manufacturers had about a 5% error rate. Better to look "good" than "bad"! Gee, I wonder how the car would run if ALL computer components were off about 5%?
We now have a 2012 and for 3,000 the error rate is still about 5%.

 

The first time I reported results in this thread was 116 fill-ups in the past. Three years later, I now believe I have a good enough collection of data to be able to come to a conclusion: The MID (or MFD) displays a higher MPG than you really are getting in your Prius.

There. I've said it.

Here are the particulars: Across 58,000+ miles and 125 fill-ups, the Multi-Information Display (MID or MFD) has shown my fuel economy to be 52.6 MPG. My calculations tell me the miles vs. gas purchased is really 49.8 MPG. Taking into account each and every fill-up, dutifully recorded, and comparing it to each and every MID readout (also dutifully recorded), I have found that the MID is 5.75% higher than my actual, calculated MPGs. (Understand that I am assuming the odometer has correctly measured my distance, and that may be a bit of a leap.)

I have the data shown on a chart attached to this post. If you have trouble opening the .pdf file, you may also check out the same chart in one of my PriusChat albums.

Questions? Anybody? Bueller?

 

Forgot to note: One thing that surprised me a bit is how the variation diminished seasonally. The MID/MFD information is a bit closer to the calculated MPGs during the summer months.

 

Hey F8L! You confused me a bit by quoting my very old message, right after my update.

I'm assuming your reference is to your lifetime data, and not just those first few tanks.

Have you noticed the seasonal variation? That was a bit of a surprise to me. I doubt you'd have much to compare it to. There's Tule fog season and the rest of the year, but you probably wouldn't see the kind of seasonal effect we have in the Midwest.

 

Did you track enough information so that you could determine whether there were such changes on your Gen II?

 

!!! I'm surprised! So you only kept the actual fill-up info and stopped keeping track of the numbers on the MID/MFD? I know you had more critical things to do, but I thought you were logging everything. (Not that it matters, of course, as it appears the readout is 5+% across the board.)

 

Whew! I thought I put miles on!