Oil pressure drops with increasing RPM, but still stays well into the green

A late, but important addition. I had the same problem, even with a fully warm engine, that got progressively worse. Finally, it turned out to be an oil hose on the section side of the oil pump which was sucking closed with increasing rpm. This starved the engine of oil ... bad news. Even after removal, there was no physical evidence of a bad hose, but installation of a new one fixed the problem.

Jeffry, how did you find out that the hose on the suction side got sucked close? During ground run with cowling off? I sometimes see oil pressure fluctuations and though more than once if a warm hose might develop a tendency to get sucked close. At least it may sort of explain the effect I see.

Peter,

Some folks use a stainless steel spring inside the oil hose where there are sharper bends to make sure the hose does not collapse.  The spring size is AN-8 (1/2”) and readily available.  You could install it as a test.  Roger Lee has some posts on this. 

https://www.summitracing.com/parts/ear-773408erl?seid=srese1&gclid=EAIaIQobChMI3cPLqLiLgwMVEh-tBh34xguuEAQYASABEgLqmfD_BwE#overview

I use springs inside the hose anytime a coolant, oil or fuel hose makes such a sharp bend that it flattens the hose out which reduces the flow. It isn't usually kinked off, but flatten slows things down. I put a spring right in the middle of the bend. I have some say that when I did this on their Flight Design their oil temps dropped 15F - 20F. I've been doing this since about 2001. Seems to be working since then. I have never had any issues doing this and I see aircraft Mfg's doing it too. Even when I see a plane again after 5 - 10 years worth of rubber changes I have never seen a corroded spring. 

Peter Kl. wrote:

Jeffry, how did you find out that the hose on the suction side got sucked close? During ground run with cowling off? I sometimes see oil pressure fluctuations and though more than once if a warm hose might develop a tendency to get sucked close. At least it may sort of explain the effect I see.

No, in flight, in the range of normal rpm. And mostly because it was the only reasonable explanation remaining. Initially, the effect was intermittent (or intermittently noticed). Toward the end, the pressure at high rpm would drop lower than before and, every time, would recover to a normal value by closing the throttle, increase as rpm was increased, then suddenly drop again. This was perhaps confused by the "normal" quick bounces in pressure that seem endemic in particularly earlier 912s. Example readings: