View Single Post
Old 05-29-2003, 12:12 AM
bobbyv bobbyv is offline
Registered User
Join Date: Aug 1999
Location: ajax, ontario, canada
Posts: 773
oil pressure is proportional to engine speed (not "acceleration") and oil viscosity. Oil viscosity depends on the viscosity rating (e.g. 15W40), and which decreases with temperature.

therefore, the oil pressure rises when you rev the engine. The higher oil pressures at higher rpm are necessary to support the increased loads on the engine's journal bearings - hence the observation of a maxed-out reading during elevated rpm. If oil pressure remained low at high engine load, you could have metal-to-metal contact within the journal bearings.

this is also one reason not to "lug" the engine, i.e., run it in a high gear at a low rpm (this applies to those with manual transmissions), since this is a high-load, low oil-pressure condition, which may result in accelerated engine wear.

the oil pressure gage will also display a higher reading at idle in winter than in summer, because of the higher viscosity of the cooler oil in winter.

oil viscosity degrades as it is used, and you can expect lower than normal readings at idle.

the oil pressure gage is calibrated in "bar", where 1 bar = 1 atmosphere = 14.7psi.

the 190e2.6 owner's manual states that a reading of 0.3bar (4.4psi) at idle when the engine is at operating temperature, "will not jeopardize its operational reliability".

the oil pressure gage is your friend ...
Reply With Quote