calculated vs. computer MPG - Please post your results

If you are in touch with Toyota you might suggest they upgrade the ODO reading to include overall FC since new similar to that displayed in the A and B trip displays.

 

I'm seeing a fairly consistent 5% variation (displayed is +5% of actual).

 

Anyone can be in touch with Toyota to suggest adding any new function.

Ken@Japan

 

I forgot to write down the displayed MPG for my 2nd fuel-up, which is why there's no data there.

But there is a range of +2 to +3.9 MPG for the display over the caculated MPG (those are the bolded numbers in black at the bottom). It doesn't seem to be consistent that higher tanks = higher discrepancies, either. I'm really hoping it's just the cold weather and bad conditions that have been making each trip slightly worse than the last (I live in the Chicago suburbs, so it's been gross here). That first trip was when the weather was around 70F, and the following week it dropped to mid-40s. From there it just went down, down, down.

 

My Level V, 17" wheels, heated leather, and Nav package is as follows...

Total miles 14645
total fuel 306.60 (41 fillups)
MPG shown 50.36
MPG calc 47.77
running error -2.59 MPG

I am tracking my stats on a spreadsheet, all fuel, services, washes, etc.

Also to note ... I have seen some post about poor tire mileage ... by actual measure, I expect my Bridgestones to go about 55,000 miles.

 

Since my purchase of 12/31/09 I've filled up twice so I could calculate the milage vs. the computer for my first 700 miles. My '3 trips' show 50,51, & 53 MPG on the computer. My Calculated from 2 fill-ups show 48.33 & 48.01 MPG - and I used same pump and stopped filling at same automatic shut off.

I drive in conservative in eco ... but have hit some hills, it's been raining recently, and did 72-77 MPH on an 85 mile stretch during this 700 miles.

QUESTION: Is there any truth to the concept that you get less MPG in the 'break-in' period??

Thanks, enjoying the drive ... and adjusting to it's minor quirks, and after 6.75 years from a bigger Hyundai Santa Fe.

Bart in SoCAL.

 

Even though I've had my car since September, I am just at 1080 miles right now. My commute is super short (about 2 miles each way) so the car never ever gets warmed up on the LA streets. Anyway, the mileage error I get is about the same as you guys.... I have been getting about 40mpg (compared to 19mpg on my old Mazda Protege with 5-sp manual) The commute is killer on any car. Calculated is about 2mpg less than FCD.

Boo Toyota!

What is good is with my SGII now properly calibrated (for fuel used after a tank full and corrected trim meter variance) it now calculates MPG spot on over the whole tank.

Most FCD's on cars suck -- but the Prius one seems to work quite well other than the 5% over estimation. Such a simple fix would make it perfect!

And what is odd is the displayed speed on the dash is already less than the speed visible on the CAN bus ... which would normally bring DOWN the MPG calculations .... not inflate them. So they are under-representing your speed and over-representing your MPG. Double-boo!!

 

The display seems to show higher MPG than the actual, although this might be due to the difficulty of filling up the tank exactly the same each time.

Here's what the display showed at the end of my very first tank. But based on how much gas, my actual MPG at 477 miles was 49.35 MPG.

 

My very first tank: Displayed 42.75mpg. Actual: 39.4mpg

This second tank will be exclusively driven with the following parameters:
-100% lower grill block
-tires 40/38
-Power mode (and try to accelerate with HSI just before power zone or no more than halfway into Power zone)

I hope the weather stays consistent to not sway my results.

 

Hi
I have filled up three times
I find my calculations 6-7% lower
The difference is about 1 klm/ liter or 2.25 MPG
So far I am getting 35-38 MPG but each tank has shown an improvement

 

Better yet, when you fill up with gas fill 5 a gallon containers up and see how close to 5 gallons you are actually getting. Alot of gas stations cheat us!

 

Our MPG offset is averaging approximately 3 MPG difference...always in Toyota's favor! Manually calculation of MPG has always been less since date of delivery in July '09.Our Prius mfg date is :05/09. I'd love to know Toyota's algorithm for calculating average MPG!

 

Our V in over 7000 miles is off about 3.75% from the calculated when we fill. It can vary from 2% all the way to 6%. I will not complain as it is still better than epa said we would get at 54.9 over the 7000 miles.

 

What is interesting is the Scan Gauge II shows, not only a discrepancy in the MPG, but also the miles. I'm not sure you all have noticed this, but because the Speedometer is 2MPH high the car is recording more miles on the odometer than we are actually putting on. According to my portable GPS my car will have 100,000 miles on it before it actually travels 100,000 by a significant amount. This might be something to check for your self. The scan gauge actually reads the correct MPH but the dash shows my speed 2 miles higher. Toyota really needs to fix this.

 

I'd agree the odometer is out by a bit too. I've only been driving 1000 miles, but initial conclusions are that the Scangauge speed is correct against a GPS, and the car reads 10% high. I'm assuming therefore that the Scangauge is correct, but it's a big assumption. The odometer (and trip meters) consistently read mileage 2.5% higher than Scangauge. I reckon that with a wheel 600mm diameter, with the tread wearing from 9mm to 1.6mm (each side) that the mileage will vary 2.5% over the life of the tyre anyway, so I'm not too concerned about that. On the basis of one tank of fuel, the Scangauge read MPG 2.5% high, and the car 7.5% high. But what startled me was the variation when measuring individual trips. I get errors against the Scangauge of +17% to -2% which seems a huge range (nearly 10mpg at 50mpg). Do other people see this level of variation?

 

I only have 5 data points. The MID is high by generally ~7%.

 

First fill up on the wifes 2010 II and the indicated mileage was 49 Fuely was 48.2. That was her first tank, and she has a fairly heavy foot so we could not be happier!

 

This is my 2nd tank results.

Traveled 541.5 miles Gas Fill 9.055 gallons

Trip MPG 62.1
Pump MPG 59.7

Fill was at 1 pip (solid) Display said I could go 40 more miles
Temps ranged from 40 to mid 60's this tank.

 

I've been logging MPG on the Scangauge and FCD on a trip by trip basis. On average the FCD reads about 10% above Scangauge, but the difference varies hugely. I assumed the Scangauge was correct, in which case there would be a standard deviation in the reading due to variations in my driving, and the FCD would have a higher SD due to this variation plus error. But both have similar SDs, so I think they have similar random errors. SD of both is about 5.5mpg, and SD of the difference is about 3mpg. I think this means that my driving style is more significant than the measurement errors, but I'm no statistician. trouble is, there's no absolute measurement to compare to.