Kim Brennan wrote:
 > if you have low voltage
> from your alternator (or are running on battery), the gauge will read
> lower. Conversely with a subaru alternator putting out 14 volts, it will
> read higher (and hence mislead you as to how much gas you really have
> remaining.)

There is a voltage regulator in the gauge cluster that only feeds the
temperature gauge and the fuel gauge.  When working properly, it
regulates the gauge voltage to 10 volts.  What the alternator or battery
is putting out (over 10 volts that is) shouldn't make any difference.

Mike