calculated vs. computer MPG - Please post your results

I've got about 1,400 miles on my 2010 II and I'm not even getting 40 mpg. The computer is telling me I'm getting 43ish but I've only gotten 400 miles out of my best tank (10 gallons filled up each time). I love the car, but the mpg has been a disappointment so far.

 

Now over 15,000 miles on our 2010. Averaged right around 50mpg for the whole year. Somewhat higher for most of the year, much lower in Dec/Jan/Feb. Latest fill was 42.2 mpg estimated, 39.8 actual, a sharp drop as temps have fallen. As with last winter, still seeing more than 20% drop in fuel economy in cold weather and the coldest month hasn't hit yet.

 

Hope this helps, I've been tracking since I purchased my Prius. The computer averages 3.89% higher than actual.

With 26,840.0 miles logged -
- 51.35 MPG actual
- 53.21 computer

 

I was getting about the same when I first got mine. I called the dealer to complain, and they suggested that I try changing to a "Top Tier" gas (Shell, Chevron, 76, etc.) I had been buying my gas at Sams Club. As soon as I filled up with Shell gas, the mileage immediately jumped up to 50ish from 40ish.

The only other thing that changed was that I also just finished the break-in period of 600 miles when I changed over to Shell. So I can't say for sure if it was the gas or the fact that I was no longer in the break-in period.

What kind of gas are you using?

 

For the most part gasoline is gasoline. The big
factor in gasoline, were talking regular grade gas,
is the addition of Ethanol.

When Ethanol is added, 10%, currently is the government
guidlines, you can expect a drop in mpg, usually 3-5 MPG.

Many states, like Oregon, is 10% Ethanol all year long.

There is a reason why some people obtain more or less mpg's than
others, in some cases driving style, weather, terrain, but in
other cases the addition Ethanol.

That is why when comparing MPG's always add to your statement if
your gasoline is contaminated with Ethanol.


Al

 

Winter weather / wind / rain / cold / northwestern Oregon.
Fuel /reg gas with 10% contamination with Ethanol.

379.6 miles / 8.156 gals / actual 46.491 / indicated 49.0

281.4 miles / 5.921 gals / actual 47.525 / indicated 50.0

In summer the mpg's would be in the 50's,

Prius cars do not like cold.

Al

 

Wow. I have driven my 2010 prius about 23000 miles. On the 75-80 MPH highways anything over 40 MPG I think is OK. Thats actual calculated mileage, not the garbage displayed on the dash. If I am driving a series of short hops, the mileage has been about 42-44 MPG . The 45-50-55 MPH distance runs have had about an average of 46-47. I would love to know how folks are actually getting the 50+ MPG that they are bragging about. I keep my tire pressure at about 36 lbs, car calls for 35. Wont push the pressure any higher, I do drive some highways. So private message me and tell me the secrets. Either that or get out your calculators. Not a person I have met in person is getting 51 MPG or better. Let alone 55 MPG on a 2010. I actually believe the older models got better mileage then the new ones. Dont get me wrong, if there is something I can tweak to get 50 MPG+ I will be willing to do it and love you for sharing it with me. I never use power mode and am not a very aggressive driver. I think with my driving style i should be doing better. The figures used by the manufacturer of any car is done under optimal conditions. I actually am on roads shared by others. I think in reality, 40+MPG is probably better then the other hybrids from what I have seen. So i guess I am doing ok.

 

I love it. The folks from the corn states force legislature that makes us use Ethanol. For cars that is. i found a guy in upper NY that actually sold fuel meant for boats no Ethanol My car ran smoother but it cost some more dollars to use it. What I gained in mileage I lost at the cost of a fill up. probably saved the wear on the engine however. Find a guy who sells marine fuel.

 

Dont know what you run in tire pressure, i run about 36 and check it regularly. Depending on traffic, I never go more then 5 over the limit.but I will go faster if I am going to get run over by the truckers if I dont. I use cruise control whenever possible. i have driven everywhere from my home in Fl to the upper mountains of NY. As far west as upper MI. The odd thing was that i think the car got fairly good milage on the mountain roads, ya, it took some work to get up the hill, but it didnt take anything to get down them.. Did notice that when i am in colder climates the milage really dropped. i was told it was due to a low emissions necessity to keep the Catiletic converter above a certain temp, so no mattter what the conditions when the converter needed to be warmer, the motor came on.

 

After 15 months driving my Prius 2010, 39 fuel tanks, 20.000km reached (12.430mi), I can attest that the displayed MFD (of my Prius) is 6.3% off (i.e. it shows a value which is 6.3% lower than actual). Max delta 9,93%, min delta 2.23%.

Since I have charted all the tanks, please let me know if you would like to know more data on fuel consumption, lifetime averages, or the such.

NOTE: the speedometer, I have a navi since 3 months, is a good 10% off more or less at all speeds :angry:

 

Finally able to get some good performance on the Prius. I just bought it about 2.5 weeks ago and wasn't getting very good mileage. I'm up in MN where it's fairly cold now. The first week I had it, it was in the single digits so that probably killed my MPGs.

I'm improving on my driving style as well getting more EV time when possible. Can't wait to see how it does in the summer.

First tank averaged 40.2 MPG. My wife has been practicing a lot for her driving test though so a lot of run time with low miles and the freezing temps didn't help.

Also considering blocking the lower grill.

 

This should be interresting. Thanks. I keep seeing 50+ MPG and I"m showing 43 MPG on my car so far. I have a Gen III with about 30,000 miles on it that I purchased a month ago. So far we've put on about 2,000 miles, mostly at freeway speeds. I'm hoping that my mileage goes up as my in-town useage becomes more of the average. I'll start calculating it manually as well.

 

Here is a link that I have found helpful:

Top Tier Gasoline

I'll be changing my gas fillup routine - my car costs so little to fill up, if I spend 10-20 cents more per gallon than I'm currently spending at WaWa I don't really care much if its better for the engine and gives me some more mpg.

 

Just did my 8th fill-up. Computer mpg showed 55.8 while hand calculated indicated 51.4, a variance of almost 8%. In the previous 7 fill-ups, the variance has been about 6%. I changed stations where I get gas on this tank so I'll do my next fill-up at the same pump to see if the variance comes back down to 6%.

 

Ack thppfffftttt !!! Just topped off my tank for the 2nd time. CONST read 58.4mpg for the trip, in reality I got 52.1 mpg. That's way off !

 

Question.
I have 2 x 2010 Prius. Blue II and White III.
I know it's not accurate, but had to ask this question.
1. White Prius shows FILLED UP 620 miles I can drive until re-fill
2. Blue Prius shows FILLED UP 444 miles I can drive unitil re-fill
This is big difference and want to ask if there's something wrong with this..
Any advise? All Prius has different display? Since it's gas station fill up, it's weird to see this drastic differences..

 

Is there any hope of a TSB correction for these calculations?

 

That would be wonderful - but maybe there is also a technical limitation. How accurately can a car determine how much fuel it is consuming? We know how much when we refuel, that is, we mechanically know how much goes in there, but the Prius, how does it know exactly how much? or better, how much would it cost to get it done to a % of exactness?

Moreover - if they change the software to be 1-2% more accurate, it might be that it shows a *worse* fuel consumption than it actually is, and likely Toyota marketing, does not want that - and psychologically it would not help the drivers as well (i.e. especially those who don't know about the 6% error, or don't calculate their fuel consumption).
All cars, also have such built-in errors, due to either cost reduction for the correct estimation of the consumed fuel, or again for marketing reasons.

In my case, as long as the error does not change over time and it will stay at 6%, it is OK. I was never expecting the MFD to tell me the *exact* truth - in the same way the speedometer doesn't... (there I have a 10% error....).

 

pakitt - Yes I'm not expecting to be identical, but it is very strange to see 176miles difference at same time filled up. Just asking if this is what everyone has issue. Since I have two same year car (same engine), I thought it is very strange to see when filled up. Almost like gas tank is different or computer errors. I don't bother looking and driving that anyways..