Toyota Prius computer exagerate MPG

I love my Prius. But:

Every tank I gas up, my MPG manual calculation from tank to tank is 5 MPG lower than Prius built-in computer display.

Green Hybrid web master should mandate all users to use manual caculation. As a group, we can see which model has an acurate MPG according to its computer display.

This is a separate issue than all hybrid cars re-evalueated every manufacturer's EPA, starting from 2008 models. Thank god they became more realistic.

Yep, the Camry in my opinion is about 1-1.5 mpg off as well. I usually add my numbers up manually - take millage and divide it by gallons of gas in car at time of fill up. I think thats how most of the people around here do it actually. I have a stack of receipts dating back to my cars purchase.

Ironically I just added another tank to the database on my TCH. For all my entries to date I've used the MPG off the TCH display. I usually refill at about 1/4 tank but today was a top off for holiday travel. Miles traveled 127 and MPG per display of 40.6 I was happy as this was above average for me and after trying some new things (i.e. no AC here in FL & 40PSI Tire pressure. But, as posted in my cryptic notes for this tank in the database:

"First Partial Tank with no AC use & after increasing Tire Pressure to aprox 40 PSI. I enter MPG from TCH display and this was much higher BUT purchased 3.495 Gallons for 127 Miles which is actually 36.337 MPG?"

Seems like a material difference to me. BTW purchased fuel where I almost always do and I always allow the pump automatic shutoff to do its thing. I have records of each tank that would allow me to go back and sample or calculate manually...and I just might....but for now I've got to burn some unknown amount of fuel. Happy Thanksgiving to all.

Silver Shadow

"Everyone is entitled to his own opinion, but not his own facts."

You better use GPS to calculate miles driven while you're at it. Those odometers can be quite a bit off.

Hey,same here.My running total on the Prius display is always 3-5 gallons more optimistic than actual.It usually reads 45-46 for the tank, but actual calculations say 41-43.
Thanks,
Charlie

A caution on using tank averages on the Prius. From what I have heard, the fuel tank bladder can make the capacity of the tank vary from tank to tank.

Best way is probably to do a tank average average (many tanks) to derive an offset to the indicated MPG. Once you know the offset, use the indicated display and offset it.

My Prius computer displays CONSISTENTLY 5 MPG more than the actual, every tank!

I bet there is not a single car, any make, displays lower MPG than manual.

I have about 36 tanks now.
For the first 20 or so I religiously compared the dash to the pump.
The dash averaged 1.4 MPG lower than the pump.

I have always entered my miles driven and gallons pumped and let the database calculate the MPG.

Funny, in my first generation Civic Hybrid, 2004, it was a couple MPG the other way.

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.

Not true! It appears that the Honda Civic Hybrid 2006-up generally displays a little less MPG than actually calculating it. My car certainly does (usually). I keep notes for each fill-up in the GreenHybrid Database of displayed MPG, Actual (calculated) MPG and price paid. Check it out.

Regardless, I think calculating it is the only (close to) accurate method.

Steve

STOP terrorism - Drive a HYBRID

Vehicles:
350 miles a week ------------ 2006 HCH II, Magnetic Pearl, w/NAVI (born on May 25, 2006)
350 miles a month ---------- 2003 Mazda Tribute ES-V6
350 miles a year (for now) - 1986 Mercedes 560SL

+1 for my 2007 Civic. It is about 1-2 mpg lower than calculated. Every once in a while, it is the same and I am dissappointed. I had a 58.8 computer reading and I thought for sure I would get 60 on manual calculation - but it came in within .1 of the computer.

I do think that most cars come in more optomistic than the screen.

I am not a database person but I would have thought that manual calculations are mandatory. If people are entering it based on the computer estimate, it sounds as if the HCH-II would be a bit better in the real world than the Prius.

My lifetime is about 52.5 computer and almost 54 calculated. 11k miles.