RE: Sleipner bow thruster
GL-4 seems to be the*best bet; according to a Castrol note, EP90 has been replaced by GL-4.* You may well end up with an 85W-90*just a slightly extended viscosity range.
Napa shows a StaLube GL-4 85W-90.
Don't go with a GL-5, even though it's supposed to "superceed" the GL-4.* Apparently some of its*additives*may be corrosive to ***some*** metals.* You may be OK, but probably would need to check with the mfr.
BTW:* "Hypoid"*means oils compatible with helical cut (as opposed to straight cut) gears.* These require oils that can handle*higher pressures - therefore the "extreme*pressure" or EP designation.* So EP, GL-4, GL-5 are all "hypoid" oils.