Series 60 Oil Leak

The flair to pipe 90° fitting is leaking at the block.
Using correctly sized wrenches or spanners, the blue hose will disconnect from the 90° like a garden hose.
Mark the 90° with a marker pen so the same angle can be found when re-installed. With a spanner remove the 90° fitting from the block.
Count the turns when removing, screw back in the same turn count. Practice this a few times to make the count repeatable.
Clean all well. Coat male threads to the block with Loctite515 and reassemble. No sealant on the flair.
I think removing the dip tube and replacing that lil hose with fresh clamps would be involved also.

I know people are scratching their heads about my spec on the 515 gasket maker on pipe threads. Been using it for years with great results.
Just one thing, don't dally when screwing in the thread. In pipe thread use, the 515 dries fast and hard.