it's likely, that you had plugged passages before, and now that you are putting fresh oil in, the motor is getting better flow and showing you the 3 bar now.
when you changed the oil, did you replace the two o-rings on the bottom of the shaft?
they will change the behavior in a positive way to how your oil pressure gauge responds to the oil pressure you have.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!