I suspect not. May take longer to warm up but what energy goes in on one side has to make it's way out the other at some point. Check the local DIY shed though, in case there is a type that convinces you.
They look as good as the day they were painted but it's always been quite a dark colour of emulsion that goes on so I couldn't give you an accurate answer. All the radiators that are still white are just the original paint.
But something washable is best .. preferably eggshell or satin. Two light coats. Brush it out well and don't try to cover perfectly on first coat (you'll see runs)
I colour-code my cottage ones with acrylic pre-packaged car colour with a matting agent, so they are low-sheen satin.
I no longer use oil based paints on radiators because they create a smell which seems to go on and on for weeks on end.
My approach is to ensure that there are no bare metal spots( if so 'touch-in' with oil paint) and then apply emulsion; be it flat, silk or satin.(I prefer satin) Dries very quickly to apply a second coat if necessary. Furthermore you will not get the discolouration associated with oil based paints; even if you use white colours. (Mine are all shades of 'off-white' )
That's what I'll do Ron. There was lot's of flaking so I sanded it down and painted the bare bits with gloss (only at the very top) I'll finish with satin tomorrow :-)
ummmm... Give the newly painted gloss spots the very lightest of a sanding so that the emulsion is applied to a 'keyed' surface. A moistened kitchen 'green pad' pot scourer would be ideal if you haven't any very fine sandpaper. In fact you could give the whole of the radiator a rub over with a green pad.