3rd Generation Prius Annual FE Statistics

I've had my Prius IIIG for 3 years and 3 months and just filled my 100th tank of gas. I've kept records for each tank of gas so I could calculate the actual mileage. The car's estimate averages 5% over actual mileage. Great mileage in the spring and fall (57+ actual mileage), little lower in summer with AC running and into the high 40's during cold windy spells in the winter. Love the car!!!
Total Mileage on Vehicle: 47017
Fuel Economy (MFD): 55.681
Fuel Economy (Calc'd): 52.955
Total Amount of Fuel Purchased: 887.860 gallons

 

I've saved data on all of my tank fills for my 2010 Prius that I purchased August 11, 2009.

Total Mileage on Vehicle: 51,728 miles
Total Mileage This Year: 2,935 miles
Fuel Economy (MFD): 55.55 mpg
Fuel Economy (Calc'd): 52.79 mpg
Total Amount of Fuel Purchased: 979.728 US gallons


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).

 

We've had our 2012 Prius 2 model since 3/29/12 and I've kept spread sheets with all data to calculate the actual mileage and variances. In the beginning I was upset because of the disparity but over the 12 month period it improved to where I am not so concerned. The car's estimate averaged 53.5 mpg, 2.73% over actual mileage of 52.08. Here are the details:

Total Mileage on Vehicle: 19,360 miles
Total Mileage This Year: 19,360 miles
Fuel Economy (dash): 53.5 mpg
Fuel Economy (Calc'd): 52.08 mpg
Total Amount of Fuel Purchased: 371.72 US gallons (@ average of $3.35 for the year, nearly $1,250, substantially less than our Mazda CX-9 of $3,500)

What I find more interesting is the remaining fuel at fillup. Generally I fill up when at the last notch and beep. Over the 12 month period I averaged 3.8 gallons left in the tank when the dash indicated an average of 73 miles of travel left. In actuality the miles left averaged 190 based upon the actual mpg calculation. Nevertheless, instead of putting a few more miles under my belt, my wife keeps leaning over to see what the dash indicates while saying "You better get gas!". Is this some sort of software issue? I'd much rather it be a little more accurate. Even if the variance was 50% less, that would still be a 100+/- mile "cushion".

 

Total Mileage on Vehicle: 69071.9 miles
Total Mileage This Year: 24101.9 miles
Fuel Economy (MFD): 63.6 mpg
Fuel Economy (Calc'd): 60.2 mpg
Total Amount of Fuel Purchased: 1147.8 gallons

Best Mileage = 71.3 MFD, 67.4 Calc'd, 752.3 miles on 11.161 gallons on 8/14/2012
Worst Mileage = 56.1 MFD, 51.8 Calc'd, 494.7 miles on 9.550 gallons on 1/11/2011

Year 1, Year 2, Year 3 comparison
Mileage Year 1 = 22095.9
Mileage Year 2 = 22874.1
Mileage Year 3 = 24101.9

Fuel Economy calc Year 1 = 58.1 MPG
Fuel Economy calc Year 2 = 60.7 MPG
Fuel Economy calc Year 3 = 61.7 MPG

Fuel purchased Year 1 = 380.1 gallons
Fuel purchased Year 2 = 377.1 gallons
Fuel purchased Year 3 = 390.6 gallons

Money for gas Year 1 = $1262.63 (US)
Money for gas Year 2 = $1516.47 (US)
Money for gas Year 3 = $1588.84 (US)

 

I also live in Northern Virginia and you are doing much better than we are! Congratulations! I wish I knew the routes you were taking! But if you are taking I66, Route 123, the Beltway, and the Fairfax County Parkway like I am, then we are on the same streets and you drive more efficiently. Do you give lessons?

 

Thanks! I attribute the good mileage from our first year of ownership to my doing weekly round trips from Alexandria to Charlottesville (495-66-29), where my wife was doing a masters. Those trips accounted for 90% of the miles from that first year. After she finished in 2011 and we moved into the district, our fuel consumption has definitely come down a few notches these past two years. These days, we're driving mostly driving between NW DC and Rockville. Probably getting around high 50s MPG (displayed) during the summer and mid 50s during the winter. Secret is to drive like a granny

 

What are you averaging Robert?

 

I intend to measure mpg averaged across several refuelings at each tire pressure setting from door post recomendations to say 42 psi front, 40 rear. Unfortunately I do not have a consistent driving pattern, so if I change pressures in a time series design there will be driving mix variability, seasonal effects, and possibly spouse vs self driving effects as random influences on each data point. Counterbalancing changing tire pressures over time will tend to remove those effects on the averages although they are still a source of error for each data point.

An alternate strategy is to change pressures during long cross-country trips on interstates and attempt to get "interstate conditions" averages for those refuelings--that would minimize the influence of driving mix and season, and I can arrange for spouse to use cruise control at a specified speed I think. That would minimize some of the known error effects but at the expense of limiting the generality of the result to interstate driving conditions using cruise control.

Any other ideas? Anybody else have the hard data to contribute? We get more data points if we use the MFD displays at the end of each drive,but they are known to be inaccurate. The refueling method has the inaccuracies of exact extent of each refill, so I will attempt to have a very consistent refueling strategy to minimize that source of error. Probably safest to have separate graphs and analyses for MFD mpgs and calculated mpgs. I will start collecting data tomorrow for the 39/37 pressures on a stretch of Midwestern interstate. Suggestions?

 

This is approximately one year:
Total Mileage on Vehicle: about 59,000
Total Mileage This Year: 11772
Fuel Economy (MFD): -----
Fuel Economy (Calc'd): 46.3 mpg
Total Amount of Fuel Purchased: 254.4 US gal

About a year ago, Continental ProContact Tires with Ecoplus replaced OEM Goodyear Assurance Fuel Max, which had gotten about 47.1 mpg over about 46,000 miles. (About 1500 miles are missing as I didn't get fuel info for them, mostly when other people were driving the car.) But there could be other factors contributing to the MPG drop, including changed driving patterns.

 

Same problem with the amount of fuel left in tank at refueling and amount of error in the "miles to empty" estimate.

Same problem with wife. She's soft, but I'm not sure it's a software issue!

Still collecting "drive around Fairfax" mpg data for the 39/37 tire pressures, but we try to minimize miles driven so it takes many weeks. The estimated mpg estimate has too much variability, so I will report the calculated when we refuel before our next trip. Cheers!

 

As I recall from discussions just after the 3rd Gen came out, people on PriusChat figured out that there are about 1.9 gallons remaining in the tank when the "miles remaining" hits 0. Now, IIRC, the Owner's Manual says something that is very obscure, but one possible interpretation is that this is what there is supposed to be.

My wife is the same way. And I have to admit that I have run out of gas a couple of times in my life . . .

 

Yes, I have too, which makes it hard to object!
Had a SAAB 93B with broken odometer and non-functioning gas gauge, so distance driving was guesswork. Guessed wrong on mid-winter trip and ran out of gas at 2 a.m. with two nieces sleeping in back seat and dissected fetal pig in trunk (biology class project). No cell phones then so had to walk through fields to nearest farmhouse to call friend. Farmer thought I was a miscreant so met me near the farmhouse with a double-barreled shotgun. Hard to be eloquent and persuasive at 2 a.m., but had to persuade him to let me in house to use their telephone to call my friend, who was remarkably good-natured about getting up and rescuing us in the middle of the night.

So you can easily understand that after THAT experience I try very, very hard not to run out of gas!

 

In the data I've collected over 3 years (and further data from the 600 and 700 mile club posts) I've found that if you multiply your Displayed MPG value by 10, that will tell you the number of miles you can drive using ~10.5 gallons of gas.

For example, if your displayed MPG value is 50.0 mpg, you can drive 500 miles and when you fill up, your car should take 10.5 (+/- 0.2) gallons of gas, leaving about 1.4 gallons of gas in the tank. The +/- 0.2 allows for pump to pump variations. This also assumes that you got a "complete" fill up on your previous fill up (e.g. the pump didn't autoshut off prematurely). Your DTE will hit zero long before you reach the 10x displayed value. 11x display is very, very close (or too late) to empty.

Hope that helps keep the adrenaline under control when your DTE = 0 and you aren't too close to a gas station.

 

This is the end of my third year of driving the 3rd Gen Prius. Here are the stats:



Here's a graph that shows the long hard struggle to get a lifetime average FE of 60.0 mpg:


Of course, it helps that the last two winters in the DC area were mild. Global warming is good for something. My personal record (PR) for a tank happened a few months ago and clocked in at 66.4 mpg, calculated. The car said it was 69.2 mpg.

It just keeps getting better.

No heat nor A/C. I use an engine block heater because my daily commute is only 12 miles.

 

Ok, for the "suburban mix" driving on stock tires the results are in and the calculated mileages were:

With Tire pressures at 35/33, we drove 679 miles and used 13.1 US gallons for 51.9 mpg.
With tire pressures at 39/37, we drove 460 miles and used 8.3 US gallons for 55.4 mpg.
So for these in-town driving samples we appear to be getting about a 7% gain in mpg, or slightly less than the roughly 8% gain for the long-distance Interstate driving samples I reported earlier.

If other folks are keeping exact records of mpg at different tire pressures under otherwise as-similar-as-possible real world driving conditions, I would like to see them. I suspect a point of diminishing returns above 40 psi based on references to lab data, but it would be nice to nail down the expected gains in mpg per increase in psi for the Prius Gen 3 so that other Prius drivers could make an informed decision about where to set their tire pressures.

 

Happy Birthday to my 2012 Four! Completed the first year, here are the stats:

Total Mileage on Vehicle: 17,647 mi, US
Total Mileage This Year: 17,410 mi, US

Fuel Economy (MFD): 57.5 (*)

Fuel Economy (Calc'd): 54.7 MPG, US

Total Amount of Fuel Purchased: 318 US Gal.


Remarks: Primarily50mi round-trip commute. A mix of speeds limits between 25-55. Tires 40/38. Used heat & A/C when needed. No crazy hypermiling, just a light foot, coast when reasonable, and regen braking whenever possible. Worst tank 47 (January), best tank 64 (July). Wisconsin weather! Lower grill blocking from Dec-Feb.

*MFD is an estimate, based on an average 5.2% high reading, from 29 of the 33 total fillups.

 

I admire all of you previous posters in trying to be so meticulous regards MPG. My 2010 will be three years old on "Black Friday", (day after Thanksgiving), so have something close to 2 months to go for that. I have used Fuelly.com to keep track of my fuel-ups, but have not done much else in my "tracking". Where I have trouble is that when the mileage isn't as good as I figure it should be, I "blow caution to the wind" & drive like I "use to" in a non hybrid car. If the mileage is doing well it encourages me to try harder. My mileage is all over the place, & actually I experienced a seemingly wierd situation just this week. I now know that what I remember, about it having been said that the gas tank on these cars is a "bladder". Must be, because you can squeeze much more into tank after the pump has shut off. YES, yes, I know you aren't to do that, but I do occasionally, and have had no bad results to date. (As an aside, when I bought my Z-71 in 2004, I asked the dealer if it made any difference if I "squeezed" in as much fuel as possible when I gassed it up, the reply was squeeze in all you want, you will have no problem! Don't know how much stock anyone should take in that, but I have done that for all these years and have had no problem...... Maybe I'm just lucky, but the poor mileage that that vehicle gets, it doesn't stay that way for long anyway! And I hate going to gas stations.
But on a return trip from the Ozarks a few days ago, I topped up in Ozark, Mo. and drove home (193 miles), & gassed up as soon as I got home. The MFD, only showed about 56 mpg for the trip home, and I would not have done well at all except I pretty much "hyper-miled" behind one or more semi's most all of the way, had a head wind!..... I had squeezed all the gas I could in the tank both before going into Branson, (where we were), (either up hill or down there, all the time), & on way home, gassing up at the same service station, here's the thing....., I got my "best ever" mileage on the way home from Ozark, 85mpg,.....and that is calculated, not MFD. As I stated before the MFD was only giving me about 56mpg, for that leg of the journey. Another problem is my mpg for the segment while in Branson was probably my worst ever! Again calculated, (the MFD, actually was higher for that segment, which I understand, as it always is), but it was only 33.6mpg, (calculated). Maybe I don't know the subtleties of charting mpg with a hybrid, but I thought I did it right, as I've been plotting mpg with my vehicles since back in the 60's......... So there you are, if you've read this far congrats! Just wanted to give all info for a good response. Thanks, L.

 

I think it was only the Second Generation Prius (through 2009) that had a bladder--and you say you have a 2010.
The variation that you are getting seems to me to be normal.
I do not hypermile, so I never get the best results you get.
As for your drive in Branson--well, I've been there too, and it has the combination of two things that kill mileage. One is very steep hills. The other is long periods of stop and go traffic. The Prius outperforms other cars in stop and go traffic because it can shut its engine off, but still, when you run the A/C and other accessories, and even if you don't, extreme stop and go kills mileage in all cars. The EPA city cycle does not account for real long traffic jams, so don't believe the 51 mpg if you are driving in them.
I don't get how Branson stays so popular with its traffic--but hey, I've been back even though I'm not a big country music fan.

 

I see you managed to maintain decent FE in our horrible AZ summer ... Any tips for a newb in AZ? You run AC only minimally or make any other adjustments?