I started keeping track eight tanks ago.

By the pump, I have used 73.920 Gallons, while the MFD calculates out to 72.975 Gallons.

The last tank is always a loose end that will be mitigated as the numbers increase, but as of now actual consumption is 1.3% greater than MFD.

This is in line with other reports of ~ 1.5 - 2.0% overestimation of MPG by the MFD.

 

some people have way too much time on their hands...

 

Personally I think the reason it's inaccurate is that it only samples data every second or two. When you first press the gas pedal, that's when fuel consumption is at it's worst, but the MFD usually misses the initial acceleration and only sees the data after the car is moving significantly. This is balanced out on the other end by the MFD seeing fuel consumption for a bit longer than the engine is actually running for, but because that's a much smaller fraction of fuel consumption it's not a balanced system, as far as accuracy goes.

 

Hi Schwa:

___Remember Ken1784’s SuperMid display in Krousdb’s 04 Prius II? It would report FE almost dead on vs. the 1.5 mpg overestimation of the Prius II’s OEM FCD and they are both tied into the same ECU taps. Some of us had a small discussion that Toyota may have actually biased the FCD in the MFD this way for whatever reason(s).

___Good Luck

___Wayne R. Gerdes

 

The SuperMid tapped directly onto the fuel injection signals, plus I'm sure it sampled data continuously rather than every 2 seconds like the stock MFD. It would be nice if Toyota could make it more accurate, it's just a matter of tweaking the code a bit so that it agrees with the real useage.

 

I don't think the stock MFD does not measure such rough 2 seconds intervals.
The MFD data is very stable and relatively accurate, but it just did not calibrated well.

The displayed mileage value is always within 2% plus or minus 0.5% which is I would like to say accurate.

Ken@Japan
http://priusdiy.fc2web.com/