I'm 'house-training' a freebie road-roller, whose OBJ+MTL imported at ~50% original scale, auto-loaded its few textures. It has four material groups for the lights, which I've duly masked and made luminous using 'super-ambient'. It has a glass/glazing material, which I've tinted green for visibility, dialled to 'mostly' transparent.

So far, so good...

Then I noticed the wing mirrors did not reflect. They do not have their own material, they are part of the main vehicle.

After studying the UV map / template, I made a mask of the 'flective' portions. I've tried applying this, but only got 'sorta metallic / gleam'. There seems no way to set a masked area's reflectivity to 'mirror'. 

Without designating the mirrors' mesh as a separate group using 'grouping' tool, is there a way to mask the main model to make the mirrors 'mirror' ?? 

This is from side where you can't see the 'mirrors' don't: Superfly, 64 pix-samples, progressive, 2xGPU, 1024 vols & buckets...

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No big deal if not, as I hope to split model at 'pivot' to allow steering and, even if I cannot hinge open the door, I should be able to split out the mirrors...