Upfixin Porsche, Volume ll

Porsche Panorama's 11-volume technical anthology can be purchased from the
PCA Executive Office at 703/451-9000 or at www.pca.org.

911 OIL PRESSURE

A Technical Question Answered

What do you consider to be an acceptable oil pressure for an early 911? I show
a cold idle pressure of 20 psi and 55 psi at 4000 rpm. With the engine hot I show
5 psi at idle and 50-52 at 4000 rpm.

Bruce Anderson: It is very common for the early 911s to have low oil pressure
at idle when the engine is warm. Many of the 911s have had oil pressure
warning lights which are set for less than ten psi. Porsche says in their
owner's manual that at idling speeds with the engine oil hot, it is normal for
the warning light to light up without risking the operating safety of the
engine. It still had this note in the Carrera 2/4 owner's manual.

Where you really need to check your car's oil pressure is not at idle, but when
the engine is warm (oil temperature 80:C=176:F) and running at 5000 rpm. For
the Carrera, the oil pressure should be above 4.0 atmospheres (59 psi), but
should not exceed 7.0 atmospheres (103 psi). Some of the earlier cars
recommended 5.5-atmosphere pressure at 5000 rpm, so somewhere between 4.0
atmospheres and 5.5 atmospheres would be expected oil pressure using this
test. Our rule of thumb check for a 911 warmed to operating temperature is 10
pounds to 1 bar of oil pressure for every 1000 rpm engine speed. Using my rule
of thumb, you are still OK. You don't really make the 4.0 Porsche spec, but
just barely miss it.