Oil Pressure

What Turns On The "Oil" Dash Light?

[BSC – 2001/6/5] The oil pressure switch on the oil cooler is only for the oil pressure light on the dash – not the oil pressure gauge. When the oil pressure goes below a certain value, the oil pressure switch on the cooler causes the oil light to illuminate. The oil pressure sending unit is located on the driver’s side of the front head – below the VTEC solenoid.

Why Does The Oil Pressure Read Low At Idle?

For 1991 cars serial number 3162 or lower, see Service Bulletin 91-008

[A/H] The specification at the engine oil pump is 0.7 kg/cm (the dash gauge reading) or (10 psi) at idle. The + – value of the gauge is 0.5 So, given all the little electrons and the hot oil molecules line up on the soft side your gauge could read very close 0 at idle. Unless the light comes on (see your owners manual) I wouldn’t worry about it. You could always install a gauge and check it at the oil pump. We haven’t had a problem with oil pressure in unmodified cars.

What Is A Normal Oil Pressure Reading?

[KH] My oil pressure is ~1.9 at idle and ~6.2 and 4-5,000 rpm. It drops about .5-1 when the VTEC kicks in.

[NM] My 91’s oil pressure goes between 2 (idle) and 6 (barely anything over idle). The gauge only goes to 8. I checked the oil and the level was perfect. Bottom line – oil pressure between 2-6 is normal and fine. As long as it is "steady" at the high and low.

[LE] With synthetic 10w30 my car sits around 2 at idle and 4.5-5.5 at most RPM. If I wail on it I can hit 6. I don’t think I’ve ever seen it go over 6; once the high RPM mode of VTEC is activated, it causes the oil pressure to drop.

Our pressure numbers are higher than spec, which says pressure should be 0.7 at idle and 3.5 at 3,000 RPM. The gauge is supposed to be +/- 0.5.

[MJ] I was using fresh 10-30 Kendall dino oil and the reading was 1.5 @ idle and 5-6 at 5000+. Now I have the Purple Synthetic we were testing for the dyno day, but it is 10-40 (oops) anyhow, it runs a hair over 2 @ idle and hits 8 @ 5000+. It must have some STP mixed in there.

Why Does Oil Pressure Drop At High RPM?

[LE] The VTEC high-rpm cam profile is hydraulically powered by oil pressure.

At a predetermined rpm (depending on several factors), a signal is sent which electronically opens a spool valve, which then directs oil pressure to a mechanical sliding pin.

This pin locks the rocker arms actuating the valves to the follower on the high-rpm cam lobe, bringing that third lobe into action and altering the cam profile.

When the rpm drops and the incoming oil is cut off, a stopper piston and return spring moves the synchronizing piston back, disengaging the high-rpm cam lobe.

When the valve is opened, the pressure in the rest of the system decreases quite a bit. If your pressure does not go down (you can watch it do this on your gauge), then your car is not going into it’s high rpm cam profile.

This is the same for any VTEC engine, not just the NSX.


Oil Pressure Never Varies

[BSC – 2001/6/5] I had a similar problem – oil pressure remain constant no matter what RPM I was running. After replacing the oil pressure sending unit (on the front head) during my engine re-do, the oil pressure gauge is MUCH more responsive with RPM.