Observations of displayed vs calculated mpg's

I've always thought maybe the error is worse because of lag time during EV to ICE transitions. Heck if I know though.

 

Chip, please elaborate on your hill driving technique. I have seen some reference to accelerating downhill and others to gliding. (I am referring to the typical urban/suburban hills, not mountains!)

 

This was discovered about 3 years ago when GenIII started to sell in the US.

I have almost 3 years record ... the GEN III has about 4-5% error always over reporting MFD mpg .... I am running per tanks and overall records. The percent is pretty consistent over different driving conditions weather speed etc ...

I was unable to determine any trend. It is not mpg but percent .. and again it is pretty much constant while my mpg depends on seasonal weather ... the error not.

 

Remember Fuelly IS calculated .. you input mile and gallons and good fully script monkey calculates ....

I only started using fuelly recently not sure where you would put the car reported results... I have those in my actually spreadsheet .... which calculates couple of othe stuff ....

Problem with Fuelly is that it summs up individual mileage and gets out of sync of the odometer reported ...

 

It is the mile... your Trip a show 450.5 mile btw 450.500000 and 450.59999999 potentially every fill up introducing on average .05 miles adds up ...

 

it is not how much mile you drive but how many reading and reseting of TripA (I use that ..)

in other words you loose the anything after the first decimal

you make a reading X.5 miles that is somewhere x.500000 and x.59999999 difference is 0.099999999999 or 0.1 so you have your error btw 0.000 and 0.099999999~0.1 averge 0.05 miles

this is not much but I can already see it ...

Just checked my spreadsheet currently 17.miles difference btw odometer and the sum of all the trip miles ....

I did not understand this when I started so I choose the mile driven method rather than Absolute odometer ... apparently you cannot switch.

 

This last sentence I do not understand what you are trying to say .... I was talking about the average error of mile reading ....

OK I just looked at your Fully data ... and now understand what you were saying you put the MFD and errror info in the notes thing.

I do not put that much info anymore ... I use CleanMPG and have more extensive notes there.... the Fuelly is new to me.

Again just checked my spreadsheet the mean error over the 78 fill up is 4.58 with standard deviation 1.29 the overall error now (all miles all fuel is 5.56 although full trip MFD was reset once so MFD is not the 36000+ miles)

 

I started to do this a couple tanks ago. Before I would just drive aggressively. Boy what a difference.
I was before getting in the 44 mpg range consistently for about a year not counting a few in the 46-47 range.
Two tanks ago = 54.8 reading, 51.7 calculated driving 455 miles and last tank I got 57 reading, 54.4 calculated driving 514 miles. This is with AC on constantly every time (I live in Phx AZ.), stock tires @ 35/33.
This tank I'm getting about 54.7 so far dash reading with 150 miles.
I'm not trying as hard as last tank, and not worrying about my MPG constantly.

What seems to help a lot is if you increase your speeds on downhills and try to glide or give not that much gas uphill like you have said, plus I would like to add, don't speed.
On the highway I go 65-70, as before I was driving in the 80's mph.

 

Change your tire pressure to about 42 F/40 R and you'll see another increase in MPGs. Probably at least 2 MPGs more!

 

I was toying with that idea the past month but didn't do it. How is the ride @ 42/40 on stocked 2012 Prius Yoko tires?

 

I am not a very particular guy about the ride, but I don't really notice a difference. What's the worst that can happen ... you fill the tires to 42/40 and you don't like it ... you let out some air to the original psi. No harm no foul!

That's the best thing about changing tire pressure, you don't have to change anything else including driving style to get better mileage. If you think it's too harsh a ride, try somewhere in the middle!

BTW - yesterday I got 70.3 mpg coming home from work (34.7 miles) at an average speed of 39 mph. Don't let the 39 mph fool you, I hit traffic. When I wasn't in stop and go traffic, I kept up to most everyone else.

 

True.
One concern would be increased wear in the middle of the tire and I think it would be easier to get a blow out.
But after reading some posts on pressure this high and higher it doesn't seem to create increased wear.
What about tire blow out? Does air pressure above the recommended run the risk of blow out or make it more likely.

Nice job on the mpg coming home from work. Is that dash reading or a guesstimate subtracting 2.5-3 mpg from dash?

 

As far the tires go, I'm not an expert on that. But, there is usually a significant factor of safety calculated in.

It's the dash reading, so it's probably about 66 real mpg. I'm usually about 6% high.

BTW - I usually drive around in the Normal mode.