I have 3 tanks of my normal mix of in-town/rural highway driving. The MPG display is very consistent through these 3 tanks reading 24.8 - 25.1 MPG.


The oddity is that my initial expected range on a tankful (ie. 50 miles driven and range 380 = 430 miles total) decreases as the tank empties such that by the time I'm at 300 miles driven, my range will now be 75 miles = 375 miles total).


Again, there this no change of the MPG reported, so the difference is somewhat puzzling.. Has anyone else noticed similar experience??

 

The range remaining number seems to fluctuate based upon a mixture of your previous trips with some weighting from your *current trip* MPG rating.

For instance - I'll pull out of the garage and it could say 300 miles remaining (based upon my tank MPG rating of 34) - then after I drive on the highway for a bit and my current trip MPG gets up near 40 the range will change to 375.

It would be interesting to hear from Honda/Acura on how they derive that number and what sort of Al Gore-ithm they use. The manual doesn't really say much.

 

I certainly presume some weighted-averaging methodology and fluctuation with significantly varying MPG conditions.
That's what confuses me - the MPG variance over the last three tanks has been < .5 MPG...I was expecting a fairly linear transition from miles driven to remaining range...

 

at Al Gore-ithm

 

Ah - I don't know that it looks at the MPG from previous tanks to calculate the current figure. My assumption was it just looks at the current tank and the current trip - but who really knows. I know on long highway trips it's definitely linear and I would guess fairly accurate. When you mix highway and city driving it's going to fluctuate.

It's funny because my wife thinks it's a real number ("I still have 40 miles to go!") so I have to always remind her that it's a best guess approximation and that if she runs out of gas I'm not coming to save her!

 

I know that most modern Acura's have a 3 gallon reserve when the computer says 0.

a dummy light, if you will.

 

I suspect you're right about how this works. It has always been interesting for me to watch this. The total range (expected range + miles driven on the tank of gas) can fluctuate as much as 100 miles at the beginning of a new tank. My range normally starts out at a little over 400 but drops quickly as I drive around town. But if I immediately start a trip, the range can jump up to 500 - 550 and then drop 50 - 75 miles as I go over a mountain pass only to go up again on the down side. As others have said, you need to take the "Range" number as only an approximation.

 

I always wondered how much was left in the tank when the low fuel light comes on because I never seem to put the full amount of the tank in when I fill it up. I assumed approx. 2 gallons because when my light comes on I normally only put about 15.5 in to fill it up.

 

The main point of three tanks is that I've shown consistent averages throughout the entire tank and each time experienced the same shift from an initial 450+ mile projection to high-300's by the time I'm under a quarter of a tank remaining.
I continue to be surprised at my mileage...I did a >300 mile trip with much of it slightly over the 80 mph speed limit and the displayed average was 33.9 mpg!!!