After doing some rough tests on engine oil pressure, when attempting to find an engine knock, it appeared that the oil pressure relief valve was operating a lot, even with a warm engine. Luckily, the engine knock was found to be caused by a faulty carburetor needle valve which was causing flooding on hot & initial engine starts.

Eventually, I got around to doing some better oil tests using a pressure gauge & sump temperature sensor, the results were a bit worrying, showing that the engine was slow to heat up, during which time the oil pressure exceeded the allowable maximum. I then changed the oil from Castrol GTX2 20/50 to Mobil 1 5W/50 synthetic and found this oil needed to be even warmer than the other oil to get engine lube pressure below the relief valve setting. In all a bit disturbing.
Test results see: prestest.gif

There seemed to me, to be a need to measure flowing oil temperature pressure and volume more closely, to give the driver an indication of when the engine was warm enough to allow full loading and exploration of the full engine speed range.

At: http://perso.club-internet.fr/chbosch/veglia.htm
There is a picture & detail drawing of a rather nice 2CV oil temperature & pressure pick up device.

I have slightly modified the adapter plate, substituted the Veglia instruments with VDO & fitted the system to the car,.
My Version of The Adapter Plate see: oilring.gif
A Line Diagram of the Electrical System see: oilelec.gif

Installation of this device allows more detailed on the road monitoring of oil flowing pressure & temperature in the system, of more interest in short stop start motoring. It is already apparent that the 2CV engine takes some time to warm up, during which, perhaps it is advisable to take it easy until the lube oil temperature are:

50ºC with Castrol GTX2 20/50 multigrade oil
70ºC with Mobil 1 5W/50 synthetic oil.