oil pressure when engine off

Pull the wire off the Oil Sender.

The panel gauge should read ZERO.

If it doesn't, there is a wiring problem.  Chaffing???

If it reads zero, measure the sender's resistance.

It should be >240 ohms.

If it is reading ~225 ohms, that is where your 4 psi is coming from!  Sender problem!

It will probably need replacement, but flushing it out with kerosene in a squirt bottle is worth a try.

Thanks Bill. Where did you get that resistance data for the sensor?

The most common sender is 240-30 ohms. 0-80 psi

You may need to look yours up if it is different.

It may be stamped on the sender's body.

But the general troubleshooting procedure will be the same.

It will at least get you pointed in the right direction!

Just found this...

https://www.dynonavionics.com/includes/guides/Addendum_Kavlico_Sensors-Rev_C.pdf

It is not a "Problem" is is a "Feature".  

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If you have a 3 wire sender.  Ignore my previous instructions.

Bill,

That Dynon document is definitely interesting, but it is talking about Kavlico sensors (is the Rotax sensor a Kavlico sensor?) and it does not refer to Skyview, only earlier Dynon systems (but they may have published a separate document for Skyview). Another thing that isn't quite right is the document says a 4 psi reading occurs with the 50 psi sensor. Surely the sensor is not the 50 psi sensor.