[pudicus]

It used to be pretty conservative where I'd hit the highway, but the read-out would hardly change until I've run up a good 6-8 miles. Yet now it goes from 16.4 to 19 to 21.5 MPG - in the span of 90 sec - while I'm driving in the city. Then after I hit the reset - while on the go - it may show 12, and then 35 or 9 MPG.
That did happen a couple of times in the past. But only after refueling where I'd hit the reset and suddenly get such funky numbers. Unfortunately now it doesn't seem to wanna go away.
I'll be taking the vehicle in for service soon where I can have the dealer look at. Ideally, though, I'd rather them not touch anything inside the car 'cause then you begin to discover a scrape here, a dent there. And the pinhead manager, as always, never knows anything about their origin.
Any thoughts ?

 

[terps4]

It sounds like you have it showing INSTANT economy, rather than AVERAGE economy. I have Navigation, so I can't say for sure. But it sure sounds that way. Does anybody know if the non-navi display has a setup for this?

-Andy

 

[pudicus]

What makes you think I ain't got the NAV :twisted: ? What you're talking about is that box on the right with the yellow business going up and down as you lay in and out of the throttle. That's your " instant economy " . While I'm talking about Average Fuel Economy read-out which is in the upper left corner.
Back when I was driving a 5-series it'd also show instant economy. Like if you tore from a red light it'd immediately show 9MPG as though you were packing a Ferrari V12 under the hood :lol: . But that's different from the FX set-up.

 

[Silver Bullet]

pidicus, I'm a little confused. Are you experiencing these swings all the time, even if you don't reset for several tanks? I only reset my average every few tanks to get a feel for overall mpg performance. When I reset it takes a while to settle in on a reasonable average. 8)

PS: on my 45 after 3 months, no matter what I do, I average about 16.5 mpg, but I've only done one road trip.

 

[pudicus]

Normally I'd reset mine following each fill-up. And it'd take a good 1/2 hour for it to go from, say, 16.9 MPG city ( i.e. granny mode ) to 18.2 MPG highway. Forget wild swings.
Whereas now it may shoot from 12 MPG to 18.5 to 22.4 MPG in the span of 3 minutes while I'm driving in the city with an even application of the throttle. Couple of times after my attempting a " corrective " on-the-go resetting to clear this nonsense, I'd end up with it showing 35MPG. What am I driving a Prius all of a sudden ?
That's why I fear something got screwed up internally.

 

[duncantuna]

I have to say I'm a little confused too.

The MPG display is an averager of instant MPG reads. (It's probably a complex formula, but averaging is certainly a great part of that formula.)

When you fill up, as you drive 5, 10, 20 MPH away from the pumps, your MPG sucks, and therefore the number will be quite low.

Once you finally get cruising for a few minutes, it slowly bounces back up to the 16-18 range. If you're on the sailing on the highway for 20 minutes, it might get to 19-20. -- But remember, acceleration kills MPG. Every time you increase speed, or go up a hill, your instant MPG takes a nose dive, and hurts the average. Since the dataset gets wiped out with a reset, those hills and accelerations are magnified tremendously, keeping the MPG display super low.

Once there's more data, the MPG display smooths out.

Your comments about it getting 35 MPG is totally explainable, as instant reads are pretty pointless. If you're going 60, hit reset, and roll down a hill for a mile, you'll hit 99 MPG. Did you really get 99 as you rolled down the hill? Maybe. Can your car sustain that once the hill ends? Nope.

 

[pudicus]

< banging on wood >

My MPG meter - it appears - has cured itself. After the last 3 fill-ups it's been displaying a consistent, realistic reading. I guess the ghost that had taken it over, now departed .