When your car is running
slowly and also when it comes to a stop, the engines is near
or at idle speed. That is often around 600 to 900 RPM.
An engine's oil pressure
depends upon several factors including the engine
temperature, oil temperature, oil viscosity, and the amount
of engine bearing wear and other tolerances. Also, if
there is an inadequate amount of oil present, oil pressure
can be intermittent and low.
If any of these parameters is
in the not good category, oil pressure may decline.
The oil pump operates directly
off the engine and will pump oil at higher pressures
(speeds) as the engine runs faster.
Therefore, as the engine slows
down approaching idle speed, the oil pressure will naturally
and correctly decline. This is normal.
You can affect the oil
pressure situation by being certain to:
-- Use only the oil
viscosity recommended by the manufacturer;
-- Ensure that there is
always adequate oil in the engine;
-- Change oil at the
recommended intervals to minimize engine wear over the
Another factor that may impact
whether or not the oil light comes on is the accuracy of the
oil pressure sensor. If the sensor is not working properly,
it may send a low signal when the oil pressure is not
Also, if the engine's idle is
dropping lower than it is supposed to, oil pressure may
decline to a point where the pressure sensor is validly
warning of pressure that is too low at that speed.