Need to know the melting point of certain automotive properties.

Specifically polycarbonate tail lights, and butyl. I'm taking some tail lights apart. Most people recommend 200°, but I see the melting point of most polycarbonate is 230°, and I know, for a fact, that a residential oven doesn't stay at "exactly" the set temp. It goes above and below to give a median temp. So if you set an oven to 200°, it can get dangerously close to melting my $500 tail lights. The inner lense is PAR or "Polyarylate"  and another lense is pmma which is Polymethyl methacrylate (melting point of 320°)

Meanwhile, butyl Stearate says it melts at 80°, and butyl acetate melts at 108°. But which butyl are we using in automotive tail lights? 
 

I know someone here is one of those chemical scientist guys that can help out. This forum ALWAYS has the answer. 

I know my omni has butyl Stearate, and a heat gun gets them out. I know a head gun will separate the lens from housing also. 

taking the lens off of the base?  I only ever put the oven on a low setting and let it sit.  Every 5 minutes I would pull and check.  The Glue generally melts before the poly

In reply to mad_machine (Forum Supporter) :

Right, but I've done this before on some junkyard NA taillights and they cracked apart at the lense when I went to pull apart. At $420 per light, I don't want to make that mistake again.