calculated vs. computer MPG - Please post your results

Just looking at your fuelly seems to indicate quite a positive difference with the switch to E0 90. As soon as the gas in this tank is exhausted, I'm also going to E0 as I'd like to keep the ethanol out of the tank but would love to see the increase in mileage as well.

 

Thanks for noticing! I actually posted a thread about it in the Prius C forums, here's a link.
It seems like most only see a small percentage difference between the two.. Not sure why I've seen more noticable results, but I'm still testing so time will tell.

I really find satisfaction when I take the time to plot all of the data like I've done, work to see a comparison and come to a positive conclusion. It's very rewarding. I think you'll enjoy E0 fuel especially with the PiP since it uses limited fuel anyway.

 

The FCD MPG is consistantly 5.0-5.5% higher than the calculated MPG. This is over 9200 miles in a 2012 Prius - level 5 with the 215/45 tires. Actual MPG is 40-44, which I assume is because I do a lot of short trips. Whenever I drive over 10 mile trips, whether highway or local streets the actual MPG is about 50.

 

Prius: 4,4 l/100km (53.46mpg)
Fuelly: 4,7l/100km (50.05mpg)

After 4800km.

 

My most recent fill-up:
Prius: 56.3 MPG
Fuelly: 65.9 MPG (492 miles with 7.469 gallon fill-up)
$3.699 a gallon, filled up $27.63 total.

I'm the only person who drove the car (sat in my garage for a week while I was out of town). I accidentally had the key with me, so no one else drove her. I drove super carefully and was pretty upset the past 2-3 days (last 150 miles) because I couldn't get the Prius MPG up. ...until I got to the gas pump!

 

This winter during cold days (less than -20 Celcius here) I ended up with more than 10% difference!

 

Fuelley 4,7l/100km
Prius 4,4l/100km
After 15 900Km

 

If you want an accurate analysis you need data - a lot of data. Here's 9 1/2 years of data across a 2004 (5 1/2 years) then a 2007 (current car). I record the fill up MPG (MPG calc), the car calculation (MPG carPC), and then chart the bias on the right axis. Average over time is 1.4 mpg off (2.6%). The car calculation shows a slightly optimistic MPG. The 2007 is slightly more optimistic than the 2004 was.

 

2004 gasoline had less ethanol than 2007 gasoline?

Agree 100% on data collection! The famous (and appropriate) Lord Kelvin quotation:

“I often say that when you can measure what you
are speaking about, and express it in numbers, you
know something about it; but when you cannot
measure it, when you cannot express it in numbers,
your knowledge is of a meagre and unsatisfactory
kind; it may be the beginning of knowledge, but you
have scarcely in your thoughts advanced to the
state of Science, whatever the matter may be.”

 

Been cruising around in my babeh Prius for about 2,600 mi, getting honked at and looked angrily at by other drivers and stuff... you know, as usual. They see me rollin', they hatin'...

Anyway, I did my math and looks like I've been getting about 51 MPG actual vs 53.6 MPG indicated, so about 6-7% difference.

I'm thinking to put more air in the tires and see if that makes any difference.

 

I have a prius c and my lifetime mpg is off by less than 1 mpg. I think that is really good. I am intrested in how some tanks are off much more, I think it may have to do with working the car to get the best mpg, and also fill ups are not exact. I feel the mpg computer should be + and -, not always +. toyota should adjust so it averages corectly, but this is really spliting hairs every car I have ever had that had mpg calc. were always off by more than this car.

 

Bought mine last week and have driven it all city miles. Just topped it off after driving about 250 miles (it's just over 300 total now so it isn't broken in) and got exactly what the sticker said, 51 mpg. Gonna take a 500 mile round trip tomorrow, all highway, so I should get a good comparison with a new vehicle.

 

I'm savoring the economy of seeing 300-miles distance on the odometer and ½-tank on the gas gauge (ie: roughly 60 mpg)! This is the first tank consumed, so *real* numbers "...to come..." upon first fillup.

 

300 miles+ at 1/2 tank is easy to do in my v and a bit higher in my previous 2010 liftback. You can do it!

 

air it the tires is one of the most important things. they allow your car to coast much easier and your mpg will climb. I have mine a 50 and it works well.

 

I recently put 91 octain in my c and I was supprised to find that my mpg came up almost 10 mpg. the temp is changing and I need some time to work it out. so I started a thread for 87 vs 91 in the prius c.

 

OEM tyres? What's the "maximum pressure" number stamped on the sidewall of the tyre?

 

That's a carry over from the old days. I was in a class back when I worked for Goodyear. Tires are radially belted. Over inflating more than about 2 lbs does nothing but bulge out the sidewalks and actually increase friction and heat. Back in the bias ply, nylon belted tires it help a bit, now adays the optimum rolling resistance is the max inflation on the tires sidewall

 

Avoiding that distortion causing reduced traction and accelerated wear from higher pressure in the past was good advice. Gauges weren't as accurate back then and topping off in your garage wasn't practical. Now, it's nice knowing how well modern tires retain their shape, even at the cold-max PSI. Home rechargeable pumps are cheap too.