The computer moves the gauge around based on RPM. Notice that it does not change position based on hot or cold oil. A real gauge would. This is a result of people comlaining that their oil pressure is "low" or "high."
From the FSM:
Engine Oil Pressure Message - Each time the
cluster receives a message from the PCM indicating
the engine oil pressure of a 2.4L engine is above
about 0.2 kg/cm2 (3 psi), or of any engine other than
a 2.4L is above about 0.4 kg/cm2 (6 psi), the cluster
moves the gauge needle to the middle of the normal
range on the gauge scale to represent the engine oil
pressure. The gauge needle will continue to be positioned
at the middle of normal range on the gauge
scale until the cluster receives a message from the
PCM that indicates the engine oil pressure is low, or
until the ignition switch is turned to the Off position,
whichever occurs first.
Engine Oil Pressure Low Message - Each
time the cluster receives a message from the PCM
below about 0.2 kg/cm
2 (3 psi), or of any engine other
than a 2.4L is below about 0.4 kg/cm2 (6 psi), the
gauge needle is moved to the graduation at the far
left (low) end of the gauge scale, the check gauges
indicator is illuminated, and a single chime tone is
generated. The gauge needle remains at the left end
of the gauge scale and the check gauges indicator
remains illuminated until the cluster receives a message
from the PCM indicating that the engine oil
pressure of a 2.4L engine is above about 0.2 kg/cm2
(3 psi), or of any engine other than a 2.4L is above
about 0.4 kg/cm
2 (6 psi), or until the ignition switch
is turned to the Off position, whichever occurs first.
The cluster will only turn the check gauges indicator
on in response to an engine oil pressure low message
if the engine speed message is 300 rpm or greater for
more than about five seconds.
My '92's gauge actually reads in PSI and it will peak our at 75 PSI on a cold morning, which is the point at which the relief valve opens. On a hot GA day it will be down around 20 PSI at idle.
