2008 RX 400h MPG average display error?
 

I have a new RX 400h (2008) and have been tracking mileage in the database. I've been entering the average MPG from the computer display. It took me a while to figure out how to reset the computer, so the first few tanks were actually reporting the running average for those tanks. However, for the last two tanks, I have reset the average MPG at the start of the tank.

At the end of the tank, when I fill up, I note the mileage for the tank from the Trip Odometer (I reset every tank) and also note the MPG average from the computer. Just as a sanity check, I also did the manual calculation of the Trip Odometer miles divided by the number of gallons that I put in. And I get a very different number than the computer! The MPG that I calculate is much lower...

Anyone experienced similar results?

I know that the variation in the shutoff point of the gas pump can cause some variability in how much gas goes in before the tank is "full". But I'm seeing around 1.2 gallons of variation, so I'm not sure if that would be due to the pump variability.

Thanks.

John

Re: 2008 RX 400h MPG average display error?
 

It is typical for the MPG gauge to be optimistic on Toyota Hybrids.

Also,the vehicle typically travels farther than the odometer reports by a small perecnt (1-2%) New tires rotate fewer times than worn tires over a given distance.

The MPG gauge on my 2006 Highlander Hybrid is optimistic on average by 4% over manual calculations. This is an average over 48 tanks of gas (600 gallons).

Re: 2008 RX 400h MPG average display error?
 

Mine is the same....

Re: 2008 RX 400h MPG average display error?
 

My computer is saying 30.2 mpg while my calculation is 27.6 mpg. That'd put the computer at over 9% optimistic. Talk about bursting my bubble! :confused: I thought I was doing so well on the mpg...

John

Re: 2008 RX 400h MPG average display error?
 

How do you account for the variation due to the fuel left, or not, in the "tank" (hybrid battery) from the previous fill-up..??

Re: 2008 RX 400h MPG average display error?
 

You fill up the tank at the same pump every time and plot an average over many tanks. The fuel that's left in the tank need not be accounted for. You fill up. You divide the number of miles you drove by the number of gallons you put in. Rinse, Repeat.

Drive, fill up, divide miles driven by gallons put into tank.

Re: 2008 RX 400h MPG average display error?
 

After 8 fill-ups, the car's MPG readout averages 6.5% better than the actual mileage calculated from odometer distance and pump gallons.

I have kept a mileage spreadsheet for years, and the Highlander so far shows less tank-to-tank MPG variation than any of my previous cars.

Re: 2008 RX 400h MPG average display error?
 

Yep, same for me. 6.5% over the real MPG. Yes the bubble burst but I really didn't expect 28 miles per gallon in 40 deg F. weather. Actual was 26.3. Life goes on. You are not alone! ;)

Re: 2008 RX 400h MPG average display error?
 

I just went through the exercise of posting our first 17 tanks of gas to the DB, from manual calculations, for our RX. After reading the above posts, was not surprised that our overall mileage is less than indicated on the trip-info computer.

We are a little disappointed in the mileage we're getting -- penciled out at 21.1 mpg -- but I think the low total can be ascribed, at least in part, to my wife's short commute, about 5 miles, and that we've only been driving it since last fall, so the bulk of the miles were over the cold (or cool, at least, in the Willamette valley) season.

If the DB mixes car-reported mileage with hand-calculated, and one is significantly different from the other, it would be interesting, on a large data set (maybe the Prius crowd) to see the averages split out for the two modes...

On the other hand, if the object of the scrolling bar charts and all is just to remind you to drive thoughtfully and help you do better, then maybe it's accomplishing its goal and the absolute numbers don't matter so much. The wife readily agrees that it works that way for her.

Benton 7may08

Re: 2008 RX 400h MPG average display error?
 

If you want to get really picky about it, you can try what I did. I went through a decent amount of effort to calibrate my odometer with a handheld GPS. I described it in this thread:

http://www.cleanmpg.com/forums/showt...?t=5005&page=2