Strange 'Range' Behavior
dave.eaton at clear.net.nz
Thu Sep 11 20:42:19 PDT 2014
it¹s actually a reasonably fraught calculation if you think about it.
should the computer average your last 20 minutes, or your last 2 - you
could make a good case for either. add to that the fact that the tank
itself is a convoluted mess of plastic shapes squeezed into impossible
spaces so the fuel readout is decidedly non-linear. with my gas guzzler,
i awlays laugh as i fill it up with 80 litres of saudi¹s finest and the rs
confidently predicts in excess of 550kms of travel. every time. i¹ve
never got more than 450 unless i¹m feathering the throttle on a long trip
whereupon i might, just might, get over 500. i¹m far far more likely to
get 352-380 kms out off a tank (around 17mpg).
having said all that, i¹ve never had a readout fluctuate as much as what
you have observed.
¹08 rs6 avant
¹12 vw passat alltrak
On 12/09/14 7:00 am, Dan DiBiase <d_dibiase at yahoo.com> wrote:
>Took my A4 on it's first road trip in a while, from Central NJ to
>Saratoga Springs, NY and back. A function of our new car having satellite
>radio, I guess...! Anyway, was surprised at the fuel mileage - averaged
>35 mpg each way - granted, it's 99% highway miles, and traffic
>was light so the cruise was set at 72 mph and hardly had to touch it.
>That is higher mileage than I have gotten in the past, by a couple of
>The strange thing was the range computation. Going up, I used just under
>half a tank of gas so I was monitoring the range closely to see how
>far I could get before I needed to stop to ensure I didn't roll into the
>driveway on fumes - second half of the tank always seems to go faster
>than the first.... ;-) When I got onto the highway, the range actually
>went up about 10 miles, which I assumed was due to the better gas mileage
>I was getting than in the little bit of stop-and-go traffic approaching
>the Northway. It kept going up for a while, then starting going down, but
>a very uneven rate, and finally sat on 235 miles for a good 20 minutes
>(during which time I would have driven about 24 miles). So I ended up
>pulling off and putting some gas in but didn't reset the computer. Got
>back on the highway and the range read 440 miles, then proceeded to
>drop about 5 miles for every 2 miles driven until it seemed to be at a
>'normal' level for the fuel I had remaining in the tank - then went down
>normally at that point.
>I always assumed that the range calc was a simple 'look at the fuel
>level, look at the mph and compute' sort of thing and don't recall it ever
>fluctuating so much.
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