I have a 3D-printed boss or adaptor to fit to a radiator grill and hold the external radiator cap.

After replacing the radiator, the external cap is now decorative only.

The print is a close but not press fit into the grill. The cap cuts itself a loose thread into the print.

I want to glue the boss to the grill. It is just to stop it rattling and is under no load.

I have two general-purpose construction adhesives to hand. Both claim to stick anything to anything and be suitable for external use.

Is one of these suitable? The Soudal one seems promising.

If not, presumably I need Sikaflex - but which one??

my go to would be west systems epoxy., this one

What filament was used to print the item? This will give an indication of the most appropriate adhesive.

I have just used bog standard superglue on PLA prints.