.................. The engine is relatively new, maybe between 100 and 200 hrs. I've been flying the same plane previously before engine was replaced and oil pressure never stayed so persistently outside of green arc. ................... It appears that problem is not seen as no-go and mechanic has 'approved' the plane as good to go. ......
Had exactly this myself! And I was amazed/shocked by what it revealed. Same thing, came in to fly a plane and high oil pressure. Shut down and enquired. Usual blah of "been like this for ages", "maint have checked it so good to go", "what are you worried about?", "Been like that
since the new engine went in so it's fine!" etc, etc.
Since I had the a/c booked - I just snagged it! Being an Aero Engineer the people I rented it from moaned but duly accepted it was my flying that I was giving up on so reluctantly allowed me to pop it over to maintenance. Lots of "I don't know why you did that!", "what's the problem?, .... i.e. trouble maker (a frequent charge leveled at
H 'n' H 
). Within an hour it was back "S". When maintenance dropped it back I just asked the Engineer who'd taxied it back over (their Boss man this time) what the "snag" had been and all was revealed. It seems all new/recon engines have the oil pressure transmitter shimmed to the max and so over-read on release. Part of the fit/runup checks is to look at the oil pressure on a test gauge once running the aircraft before release and to then remove the required no of shims until a/c oil pressure shows the test gauge pressure. Disconnect test gauge and the jobs a good ‘un! Quite simple.
There were some very red faces tho as (a) the owners clearly had never gone back to ask about it/snagged it despite their claims that they’d checked and that the Engineers were happy, and, (b), it also seemed a certain pair of bods in the Maint facility had just had a “Chat, less tea, less bikkies” with their Boss for not doing the approved install process and then signing it off! He assured me the rest was OK! Good job as, again in this case, it had flown a good number of hours (100+) since the donk change! Bonus was, when I then did a short hop in it with the time I had left for my slot – it was called an “Air Test – have this one on us!” by the owners when I got back.
Not sure about your case
CFO, but I know where me money is with this one too! Cheers,
H 'n' H