Ford 2003 Mustang Workshop Manual page 850

Engines need oil to lubricate the following internal components:
cylinder block cylinder walls
pistons and piston, pin and rings (6102)
intake and exhaust valve stems
intake and exhaust valve guides
all internal engine components
When the pistons move downward, a thin film of oil is left on the cylinder walls. As the vehicle is
operated, some oil is also drawn into the combustion chambers past the intake and exhaust valve
stem seals and burned.
The following is a partial list of conditions that can affect oil consumption rates:
engine duty cycle
operator driving habits
ambient temperature
quality and viscosity of the oil
Operation under varying conditions can frequently be misleading. A vehicle that has been run for
several thousand miles on short trips or in below-freezing ambient temperatures may have consumed
a "normal" amount of oil. However, when checking the engine oil level, it may measure up to the FULL
or MAX on the oil level dipstick due to dilution (condensation and fuel) in the engine crankcase. The
vehicle might then be driven at high speeds on the highway where the condensation and fuel boil off.
The next time the engine oil is checked, it may appear that a liter (quart) of oil was used in about 160
km (100 miles). This perceived 160 km (100 miles) per liter (quart) oil consumption rate causes
customer concern even though the actual overall oil consumption rate is about 2,400 km (1,500 miles)
per liter (quart).
Make sure the selected engine oil meets the current recommended API performance category with
SAE viscosity grade as shown in the vehicle Owner's Guide. It is also important that the engine oil is
changed at the intervals specified. Refer to the vehicle Owner's Guide.
Oil Pressure Test
1. Disconnect and remove the oil pressure sensor (9278) from the engine.
2. Connect the Oil Pressure Gauge to the oil pressure sender oil galley port.
3. Run the engine until normal operating temperature is reached.
4. Run the engine at the specified rpm and record the gauge reading.
5. The oil pressure should be within specifications; refer to the specification chart in the
appropriate engine section.
6. If the pressure is not within specification, check the following possible sources:
insufficient oil
oil leakage
worn or damaged oil pump
oil pump screen cover and tube (6622)
excessive main bearing clearance