I asked this ? on another forum, but only Pruis owners replied.
We have the audiophile/nav system, which calclulates mpg average for the lifetime of the vehilce. I was wondering, for those of you who have this too, do you report your mpg on this site as the lifetime average, or do you reset it each tank and report it tank by tank? Does it even matter?

June

 

I put data in for each tank. (Although I don't have the NAV so I don't have a choice really).

 

Does the Nav system really store the data for the lifetime of the vehicle, unless one presses "reset"? I thought it only stores the last 2,000 minutes or something like that.

 

I enter each tank and the corresponding mileage into the DB. I do not rely on the NAV as it overestimates fuel economy by about 2mpg.

Also, as pointed out, the NAV only stores 1,000 "data points" though no one has really confirmed whether that is minutes, seconds, etc. Regardless, it is NOT a lifetime average so it is not an accurate measure of anything but recent fuel economy. (the data point measurement might be the reason that the NAV mileage is off for a full tank)

 

That is good to know. I had never the nav system reset itself, but then again we don't even have 3,000 on the vehicle yet. Must have happened while my husband was driving

 

I've found the Nav estimates just like any other system. Most of the time, mine is within .2 of by hand. Sometimes it's lower then by hand, sometimes it's higher.

The Nav system stores the last 2000 data points, which it uses it's own criteria for what a data point is. Suffice to say, it's good for a tank, or even a long solid trip, but not for a lifetime. Personally, I reset it and the trip odometer each time I fill up.

 

As you know from my 100's of posts... I am very diligent when it comes to recording mileage, and I pay attention to very small details.

My Navi also reads high 95% of the time, and most people would agree.
So it is apparent that there is some built-in bias on the high side for some reason.

Of course there are exceptions.

 

I have never trusted factory gauges in any of my vehicles, no precision. In my last 240sx I ran a datalogger and was amazed at how far off the factory guages were. After awhile i removed all of the stock guages and mounted the datalogger in the center of the cluster. Then I ran engine vital gauges in the DIN panel below the radio and on the A pilar.

 

When I was entering data I did the calculation manually (miles divide by gallons) as I figured that would average out best over time. I've been distracted and have not submitted any info in a long time, but I have recently noticed by NAV mileage increasing lately, the past two tanks over 30MPG for the first time...it just gets better with age!