A leak down and compression test won't show anything, unless something is BAD wrong like, a blown head gasket, piston missing half its crown, ring lands collapsed, etc.
The majority of these issues come from bad valve guides, bad valve seals, or intake gasket leaks. With the amount of mileage that you have, I'd be checking valve seals and guides, but you can easily do that with a scope. If the valve stems and heads of the valves don't show
oil on them, then you know the problem is somewhere else.