For quite a while now, I've been worried about low oil pressure. First noted about 2 years ago, just under 1.25 bar (about 18 psi) at hot idle. Pressure sender was a bit flaky though, so it was replaced along with oil change 1 year ago. However, the new sender showed even lower pressure at hot idle, sometime briefly triggering low oil pressure light when coming to a stop at traffic lights. Following recent oil change using slightly more viscous oil 5W-50, oil pressure is even worse, typically dropping to zero at hot idle. However, no noise from bottom end and no valve train noise. Low oil pressure warning is now coming on sometimes with engine coolant temp of only 70 C. Oddly, on these occasions it will hold 2 bar for 10 seconds or more then suddenly drops to zero. When this occurs, there is a subtle change in engine or exhaust note. At 90 C with zero oil pressure at idle, if I stop the engine then restart, it can hold 1.25 bar for a while before plummeting to zero, again with a slight change in engine/exhaust note. I can't figure out why it does this. Oil pressure is relatively low across the rev range and this hasn't changed recently. I get 2.5 bar (about 35 psi) at 2000 rpm with engine hot. I had a local workshop do a direct pressure measurement: It showed 90 psi on start, steadily dropping to 18 psi at hot idle. After short road test, 18-25 psi when hot. Oil pressure responds well to rpm, maxing out at 75 psi. They noticed some air bubbles on the dip stick. Therefore, I think next step is to take the engine out to inspect lubrication system. If that's not the problem, then engine rebuild... For engine removal and reinstallation, is an SD2/3 needed? I'm thinking of having the local workshop do the job because the only Maserati independent mechanic here doesn't seem interested. The mechanics at the local workshop have worked with V8 supercars teams, and they are prepared to do the job.