You could measure it with a inches of H2O gauge at the oil filler or dipstick. I has got be virtually atmospheric............. maybe 10-20 inches of H2O as a guess.

 

Wouldn't it be measured in inches of mercury (in Hg)? Why is it inches of H20? Is it because oil is a liquid? I'm just trying to wrap my head around this.

This must be why I never got a Ph.D. in physics (or even passed a single class in physics, ha).

 

I would look at making a barb or Tee to use the oil pressure switch to measure the pressure. Going through the dipstick isn’t pressured enough unless you go to the base of the dipstick where it enters the block.

Bar pressure sounds more accurate as opposed to in H2O or in HG. Also didn’t pass physics.

 

I would look at making a barb or Tee to use the oil pressure switch to measure the pressure.

....and FYI @CorollaFromNumi, when you reinstall the oil pressure switch into that part of the engine's aluminum block, it is only 11 ft lbs of torque. We have another forum member who torqued it too tight and is now going through a quasi-nightmare because of it.

 

28 inches of water is 1 psi which is pretty low. The way I read the question is basically what is the pressure in the oil pan or essentially crankcase pressure? Maybe I am wrong.

Mastering Crankcase Pressure: A Comprehensive Guide for Internal Combustion Engines

Crankcase pressure is a critical measurement in internal combustion engines, indicating the amount of blow-by gas escaping past the piston rings into the

techiescience.com

The normal crankcase pressure readings can vary depending on the type of engine and its specifications. However, in most cases, the normal range for crankcase pressure is between 0.5 to 2 psi (pounds per square inch) or 3.4 to 13.8 kPa (kilopascals).

 

I just base it on the compression of each cylinder. As long as the compression within the cylinder is in range, no issues to look further into at that point. Only dig further when one cylinder is lower by 10% or more.

I’d just put a tee on the oil pressure sensor and throw a gauge on it.