This is a Jet Engine model made entirely in Blender 2.8.  Model polycount is 2,1 million polygons.  Some repeating elements are done using collection instances.
Blend file, FBX and OBJ file included.
OBJ polycount is higher due to instances being frozen to regular mesh objects.  
Polycount for OBJ is 3.9 million polygons.  FBX is about half the file as the OBJ.