Re: MPG manual calculation a must!
 

There's something I've noticed, about the information displayed, tho I have no research to back it up: The 1st 100 miles or so seems to set the stage for the rest of the tank.

Re: MPG manual calculation a must!
 

Maybe the point has been lost through all these posts, but I was just trying to calibrate my odometer so I would know, as accurately as possible, my fuel economy--just because I wanted to. I was never trying to say that knowing elevation is critical to good fuel economy.

Re: MPG manual calculation a must!
 

OK.

Nice discussing this with you.

Re: MPG manual calculation a must!
 

It may seem that way because when there are only a few miles on a tank it is easy to change the MPG average of that tank with a good or bad trip.

As you put on more miles it is "harder" to change the average, because there are already more previous miles being averaged with that same good or bad trip.

Re: MPG manual calculation a must!
 

I filled up today and found I avg 51.4 mpg. The display showed 51.5. That close doesn't happen very often.

Re: MPG manual calculation a must!
 

What's a bladder! Why?

My Prius is getting funny, and worse. It was cold this past two week. But what's that to do with fuel capacity?

I can only fill up to 9.3 or 9.4 gallon from no gas at all. When I saw someones' figure in this database filled up to 12.6 gallons, I think they are faking the numbers just to get to the top of the list.

In Toyota's users' manual, it stated 11.9 gal capacity.

Re: MPG manual calculation a must!
 

In some cases, I've had to combine two fill-ups in one entry because I'd forgotten to reset my trip meter on a fill-up. It happens. The simple solution is to just wait until the next fill-up and use the combined fuel, two tanks, with the one trip meter reading.

Suspecting my tank capacity had fallen a bit with the recent cool weather, I decided to run a capacity test by running it out of gas. The engine ran out of fuel at the traffic light that crosses the main, north-south parkway through town and the master failure light came on. When the traffic light changed, I calmly drove half a block to the post office on battery, did my business and then poured one gallon from a spare can into the tank. The subsequent refill took 10.52 gallons plus the one gallon spare can for a total tank capacity of 11.52 gallons.

Also, only the North American Prius have the bladder tank. The European and Japanese Prius don't have the bladder and they can hold more fuel. I've run out of gas now over two dozen times and if I ever have a single tank fill-up come in at or over 12 gallons, I'll be calling the state gas pump inspector with a complaint. About 15 years ago, someone had a put a chip in the pump that let them charge more for less gas. People went to jail on that one.

Bob Wilson

Re: MPG manual calculation a must!
 

Odometer setting can be off a bit on any car. I've found that using the ScanGauge provides very accurate calculations vs. manual over several tanks. But first, set the speed on the SG using a GPS on "FLAT". ground. Going up or down a hill skews the reading, because GSP measures distance across the earth, very accurately.

Then when you fuel up, ensure that you set the actual gallons per SG instructions. Keep track manually for 2 or three fillups (car sitting flat, stop at fuel shutoff), then compare the total gallons used on the SG tank totals and your paper.

I've found this to be more accurate than the AVG MPG display on my 08 FEH AWD. But I'm still from the old school, and manual calculations over many tanks is the tried and proven most accurate method over any other method.

Re: MPG manual calculation a must!
 

I don't think it really makes that much difference because it's practically impossible to calculate TRUE fuel efficiency with these cars anyway.

This is because all calculations are in miles per gallon, mpg.
But to calculate mpg you must have either miles or gallons or both as a positive integer over the course of any given trip or distance.
How does one measure fuel saved while the car is NOT moving and the ICE is stopped?
This savings cannot be expressed as mpg. It can only be expressed as gallons saved over TIME.

With hybrid technology, the car is the energy equivalent of a parked car over a portion of every trip. There is no mpg measurement for a parked car.

To measure mpg at least one of the following MUST be true:
a) The car is moving with the ICE running.
b) The car is stopped with the ICE running.
c) The car is moving with the ICE NOT running.

Condition "c" can only be integrated into a "trip total" as its "measure" otherwise has no meaning. This is why the Prius internal computer will register a "blank" column in the computer graphic displaying trip history if no gas is burned.

Re: MPG manual calculation a must!
 

Fred, you are over analizing things. ( pun intended )

If you drive 500 miles and use 10 gallons of gas, your car got 50 miles per gallon of gas. It does not matter if you had 1 mile of EV, or 100 miles of EV. It does not matter if the car is standing still for 1 hour per tank, or 10 hours per tank.

The bottom line is, your car got 50 MPG.
This is a very precise, accurate number.