I see heater core replacements made out of aluminum or copper. What was OEM, and which is preferred?

Who knows if they have an original heater core any more, but mine was copper when I bought the car. I suppose both would work fine.

The OE copper model works best. I replaced an original with the little thin aluminum aftermarket part and although it was more than adequate for FL and GA, it didn't deliver as much heat as the original did. The copper core delivered so much heat I couldn't hold my hand close to the vent very long. That would probably be more appropriate for Nebraska Winters.

If you want the copper/brass core, you need to check carefully when buying. When I had to replace mine (88 GT a year and a half ago) the first one I ordered showed a photo that was copper/brass, but what I received was aluminum. I did finally get a real live copper/brass one on Amazon. It's still listed there:

https://www.amazon.com/gp/p...ilpage?ie=UTF8&psc=1

I personally think aluminium would work as well or better than copper and brass (does in radiators, which are doing basically the same thing) but I had to bought three total parts to get the copper/brass one. The two aluminium ones sure looked identical to each other but were branded differently, and I used the copper/brass one because the aluminium ones didn't fit very well at all. They were slightly smaller than the original and wouldn't install.

This Is Not as simple as Material used.
Aluminum heater cores can be same, better or worse Performance then OE Brass because Performance depends on many things.
Example: Fin density alone effect heat transfer to air. Too little or Too much fin space and air doesn't heat at low or high or any blower speeds.

Regardless of Material, If new one is not an exact fit replacement then you likely need to adjust the fit or air "leaks" can bypass the core reducing heating same as heat/cool door problems or just that door set to cool.
That's ignoring many are missing foam "gasket(s)" around the pipes to the core/ac going thru the heater box front and other problems. That can kill heating and/or cooling by letting air to move in the wrong places.

Brass/Copper cores are made of stamp flat metal then soldered every where. Most times the solder failed at a thin spot and leaks.
You may think is better but wait a few years to often have same failures. More so if you have weak coolant mix. Worse if new brass cores have Lead Free solders to meet RoHS etc. RoHS and related rules/laws not limited to electronics for most things made now. USEPA and others have new rules affecting how most things are made like This is why most "Semi-metallic" and other Brake pads/shoes are or have moved to low copper formulas.

I haven't seen let alone test Fiero AL cores to tell if they have problems or not. You can't trust catalog/online pictures.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Thanks for all your input. I'm kind of an OEM guy, so I'll look for the brass core. I know, there are no guarantees. Let the buyer beware.