Oil Gauge Fluctuations

[CarlC]

Since the engine rebuild and oil cooling upgrade last year there has been some strange oil pressure gauge fluctuations.

At idle, oil pressure is normal @ 40 psi.



At cruise, the oil pressure is centered around 55 psi @ 2100 RPM, but the needle flutters +/- 20 psi so fast that the needle is a blur.

Under coasting conditions, the needle fluctuations are less (+/- 10 psi), but still very apparent.

Here's a list of the before / after changes:

Changed the stock gauge feed plastic tube to a -3AN. The guage is a stock GM console gauge.
Oil pump from HVHP to Mellings 555
Elimination of the oil bypass to allow for CV Products oil filter adapter (no bypass)
Addition of lines and fittings for cooler (several unwanted, but needed 90*'s)
Addition of remote oil filter mount.
Addition of an in-radiator oil cooler.
Milodon 5 qt pan to CV Products 8-quart road racing pan
CV Products oil pan pickup.
Engine rebuild included new main and rod bearings.
10W-30 to Mobile 1 15W-50 synthetic.

The engine runs great, has no funny noises, and during oil changes there have been no abnormal particles.

Fatigue life of the gauge is a concern since I'd hate to have the gauge fail in the car. The other is if there is a high-frequency pulse in the system, what will it affect? Fatigue of the in-radiator cooler? Oil film thickness? etc.

Any ideas would be great.

Thanks.