calculated vs. computer MPG - Please post your results

Multiply by 0.833 to get Colonial miles per gallon.

 

I've always seen a two-three mpg discrepancy. How do you folks do your calculated - do you stop the pump at the first click or what - how do you determine you're filling to the same amount each time?

On a related note - has anyone noticed the fact that the fuel level display goes down a bar or two, then goes back to full? It doesn't seem to be related to incline...

Thanks!

 

After 4,500 miles, I find the computer mpg to average around 2.5 mpg higher than my calculated mpg.

 

My first 3 tanks, all this month were:

50.5 mpg MID 50.5 mpg Calculated (Dealer Tank)
53.7 mpg MID 51.1 mpg Calculated
54.3 mpg MID 52.7 mpg Calculated

Date of MFG: 02/2010

I always fill up with 2 pips showing on the guage and I fill one click after the auto shut-off.

Nolo

 

After eight months and 11,000 miles, my displayed mpg averages 3.3 mpg higher than my calculated at the pump mpg. I figure this to be a 7.1% error.

 

20 tanks:
Computer= 56.6 / Calculated= 54.8
Best 67.2 @343 miles
Worst 44.6 78+mph @225 miles
Hubcaps removed, mud flaps added 3 tanks ago no change in mpg.

 

2010 Toyota Prius III with Navi

5,000 miles and about 45 mpg...tried many driving techniques and even 40psi, cant get better gas mileage...

 

Yeah, I've seen the gas gauge go down a pip and then go back up, too. What is that all about?

 

First fill-up tonite - indicator said 54.1, got 9 gallons and 468 miles for 52 actual. Salesman said he "filled it up as far as he could" so I did the same, let it trip the auto shut off twice, so I think that's pretty close to as much as it would hold.

Looks like a 2MPG diff, which seems to be a lot of peoples' experience.

Built 11/09

 

We have a 2010 V and now have 8500 miles. The computer always reads high. It is between 2-4 mpg higher than actual. Today actual for 512 miles was 53.3 and computer said57.3mpg. Normal is between 2-3 difference. Our average on the computer for 8500 miles is 54.8 mpg. Even with the 2-3 mpg error it still is great mpg. I really don't get to upset with the computer error as long as we average over 50mpg.

 

how many litres in a US gallon ?

 

A Google search calculation for "1 gal in liter" returns:

 

I just did the first fill-up. Computer MPG is 54.8 as against 53.7 actual. Driven on local roads with lots of ups and downs. It's mentally challenging to drive Prius especially after my jackrabbit style in a Corolla (1993 manual) that gave 38-40mpg on the same roads. Still drives corolla 3 times a week and Prius 2 times for a daily commute of 46 miles.

 

On my 2010 version 111/IV at 700 Kilos I used 1 tank about 39.xx or for what gas tank it is rated for, can some one tell me my US MPG. Thanks

 

My last three tanks were :
57.4 MID, 55.02 calculated, 2 Pips at 491 miles
60.2 MID, 57.25 calculated, 2 Pips at 525 miles
59.8 MID, 57.59 calculated, 1 Pip at 531 miles

Overall mileage is 57.06 MID, 54.26 calculated which is a 2.8mpg difference, so 5% variance. I fill 1 additional click after the auto shutoff. So my calculated mpg average is higher than the 50 mpg rating but lower than the optimistic prius computer.

 

After 5 fillups actual mileage = computer avg for the tank * 0.91 +/- 1%

 

If I'm translating what you are asking

700 km driven
39 Liters of petroleum used.

(700 km)*(0.62 miles/1 km) = 434 miles
(39 liters)*(1 gallon/3.79 liters) = 10.29 gallons

434 miles/10.29 gallons = 42.2 miles per gallon.

 

179 miles, 54.8 indicated / 51.8 true.

Also tank was filled to brim to brim no guess work


alfon

 

It is NOT good to fill the tank up the neck and to the brim. You should stop filling after one click. The reason is that the emission control systems include [ame="http://en.wikipedia.org/wiki/Onboard_refueling_vapor_recovery"]vapor recovery system[/ame], which routes vapors from your gas tank through a charcoal canister (or similar). If you fill the tank all the way, this vapor line can fill with fuel, soak the canister, and ruin it.

(Sorry if I sound like a nag, just trying to help)

 

I did this to get a absolute true reading .

This is more accurate than the first click at the pump, also I do not do it on a
regular basis.

Just for those who have never completely filled their car, after the first click you can get about 2.1 gallons in the tank before it 'brims".

alfon