MFD MPG Displayed Number - Could this be fairly accurate?

<div class='quotetop'>QUOTE(daniel @ May 27 2006, 06:31 PM) [snapback]261898[/snapback]</div>

I would guess. You obviously can manipulate the temperature to your advantage for a one tank MPG. I am becoming more and more a promotor of the three tank average. Levels out a few of the up and downs.

 

It's amusing that in most posts in which both pump MPG and MFD MPG are reported the pump MPG is smaller. One explanation is that the MFD is overstating MPGs (maybe to make us penny-pinching treehuggers feel better?). But it would also be explained if gas station pump meters overstate the amount of fuel they pump; this of course would also increase the gas station's profit.

How much error is permitted by each state's weights and measures testers, I wonder?

 

The California folks point out that their state doesn't do the weights & measures inspecting typical of other states. One guy mentioned that he put 22 gallons into a 20 gallon tank. Ouch!

I'm under the impression that both Virginia and Maryland are pretty good about sending out inspectors to pump gas into a measuring can (or similar) on a regular basis.

 

<div class='quotetop'>QUOTE(daniel @ May 27 2006, 10:46 AM) [snapback]261758[/snapback]</div>

Actually, John & I disagreed yesterday on which was more accurate (in the FE thread: http://priuschat.com/actual-VS-computer-t20329.html). He said "If you want an overall "lifetime average", the on-paper calculation based on a collection of at-the-pump measurements is the only truly accurate method." He suggested I check out his 117k miles of data. I did so, and his lifetime numbers for two vehicles was the following:

Vehicle____Miles__Hand__MFD
01 Prius__59,827_45.48__47.49
04 Prius__57,117_48.69__49.98

His followup questions:
What is the precise size of a squirt of fuel, under each type of operation condition?
To what digit are the calculations carried before rounding or truncation occurs?
Seemingly simple tasks get really complicated really fast. So the level of accuracy we enjoy we difficult enough to achieve. It's darn close. But expecting it to be dead-on isn't realistic.

Good points, all, but I still think the onboard computer is more accurate than judging, say, the precise size of a squirt of fuel than a gas pump, which rounds digits to the nearest cent, etc.

 

<div class='quotetop'>QUOTE(sharkmeister @ Jul 24 2006, 07:33 AM) [snapback]291389[/snapback]</div>

Enforcement varies by counties in California.

In Los Angeles County the enforcement is quite stringent.

L.A. County Department of Agricultural Commissioner/Weights & Measures