This is a model I created based loosely on the Eurojet EJ200 Turbofan Jet Engine.  Originally the final model consisted of around 4.3 million polys but through some optimizations and instancing of some repeating elements, the model is a little over 2 million.  It definitely could be further optimized but Blender handles the model beautifully.  (OBJ file when exported freezes instances into regular objects so OBJ will be larger file).  I've included an FBX version as well.

All of the parts of the object are split into collections based around their Material ID or whether they were to be instanced as collection instances.
All of the parts have been UV unwrapped.

The model does not include texture maps but uses the principled shader which is shown in the product renders.  Purchase includes both a Blend File and OBJ file.
Feel free to ask any questions on the model.  A portion of sales on this go towards funding Blender Development.  Thank you!