You may be chasing a ghost. The owner's manual for my '88 specifies 0.3 bar as minimum oil pressure, but it usually runs 1.5 in mild weather and I've never seen less than about 1.0. Reducing oil pump volume flow is a trick that many OEMs use to reduce parasitic loss, and 5 psi is sufficient for idle when there is virtually no load on the bearings.

Look in the owner's manual and see what it says about oil pressure.

Duke