For the mileage computer, try a bottle of Techron fuel-injector cleaner.
I think sometimes dirty fuel injectors don't close completely and they drip
excess fuel into the motor that the computer isn't aware of... so it reports
less fuel used that what actually went into the motor.
My computer worked much better (within 0.1 gallons of actual) for a few
tanks after cleaning the injectors... but has slowly gotten worse (off by
about a gallon per fill-up) again. I think I need to run them through the
real ultrasonic injector cleaner.
The other thing that could screw it up is if your fuel pressure is a
little to high. The injectors will spray more fuel than the computer thinks
they are... so it will come up short on the "fuel used" calculation.
I would try Techron injector cleaner first... then have the fuel
pressure checked if that doesn't help.


"Ted" <miamitedNOSPAM@bellsouth.net> wrote in message
news:yBu_i.3407$2n.770@bignews8.bellsouth.net...
> My mirror always shows either south or southeast regardless of what
> direction. The trip computer shows less gas used than I actually did, thus
> the mileage and miles to empty are wrong.
>
> What could cause this?
>
> Thanks
>