I just maintain low rpm until the pressure will stay below about 5 bar, where any risk of a blown oil canister O ring is nil.

Nearly 2 bar at idle (800 rpm or so) is exceptional. Most engines need 1000rpm to achieve that (the pressure rises very rapidly from 750-1000 rpm-not linear at all).

Bob

I added an oil pressure gauge to my CS and I want to confirm the "normal" oil pressure on these engines.

After the oil is warmed up (it takes about a half hour of driving to get to 95C), the idle pressure is 1.5 to 2 bar (21-29 psi) and at 3000 rpm is about 4.5 to 5 bar (65-73 psi). Cold start pegs the needle at 5+ bar at 1500 rpm. This seemed great to me by the standards of other engines and the specs in the blue books (dead on), until I read the CS owner's manual.

The CS owners manual (page 84) says that the pressure relief valve in the filter housing opens at 2.5 bar. This would mean the oil pressure never gets above above 37 psi. I'm not sure I belive this. I'm having a hard time getting good nominal values for oil pressure since BMW rarely (read never) puts an oil pressure gauge on any M10, M20, M30 engined car. The mechanic at my local BMW shop says that idle pressure should be 15 psi and the relief valve should cut in at 50 psi. He said that the failure mode for the relief valve in the pump is to stick closed and cause the pressure to shoot past 150 psi when cold, thereby blowing the oil filter o-ring. Says its very common on M30 engines.

So what's the experience of those who have oil pressure gauges? Do I have a stuck relief valve somewhere? Should I get a 10 bar gauge and consider this normal operation? Is this a well known misprint (both bar and psi) in the owner's manual?

Devinder