I just restored all the weather strip seals today on my 87 GT and SE and it feels and looks great...I used CASTOR OIL. Way back I read a posting on one of the Fiero forums where someone recommended castor oil. He worked on fighter jets and they used it on the planes' rubber seals. As he pointed out, the castor oil is absorbed by the rubber making it swell a bit regaining pliancy, thus preventing cracks and restoring its original seal quality- great to stop air leaks around windows. You can get it at any pharmacy for a few bucks. For those of you who have T-tops, it works great on its seals-I can attest to that since one of my Fieros is a T-top.
Just apply with a soft rag let it sit overnight on the seals to allow it to absorb into the rubber and wipe off any residue the next day.

quote Originally posted by vitog44: the castor oil is absorbed by the rubber making it swell a bit regaining pliancy

That process is called imbibition and it is also what happens when someone runs out of brake fluid and pulls a "McGuyver" by putting transmission fluid in the brake mastercylinder reservoir. The transmission fluid is absorbed into the rubber seals (because of smaller molecular structure than that of the rubber seals) causing them to swell and distort beyond use leading to brake failure and the need to replace everything in the brake system with a rubber seal.

One application may not lead to any problems, but at some point if you continue on a regular basis that may change. Some stop leak chemicals work by that principle and more often than not are temporary fixes that can make matters worse in the intended application.

I'd be careful.

Yes..I'm glad you commented on my post. I neglected to mention that this should by no means be a weekly nor monthly routine. The last time I did this on the cars was five years ago.

It's been years since I've seen anything about the sunroof seal. The process I and others have used is to clean the seals with Simple Green, then a light coat of Castor Oil, let dry overnight as you suggest then wipe them very well, else the oil will smudge on the window. It's kinda hard to get off, and can migrate to other areas through touch.

If you clean and replace that often might be ok....

Castor Oil and other "organic" oils can go Bad, AKA Rancid.
Cleaning up rancid oil/grease is not fun.
If you ever clean a Grease Trap in a commercial kitchen... part of the horrid smell is cause by rancid oil and grease.
Even if doesn't smell allot, rancid oil/grease can be very sticky and very hard to remove even when you have best degreasing cleaners or solvents.
Is similar to same problem as bad gas can cause vanish etc to car parts.

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Yes. I did learn from my first experience when I noticed the windows smudged with what looked like soft rubber on them and it took some rubbing to get it off. Since then I make sure-as you point out- to remove any oil residue the next day. For 28 year old cars, the rubber seals are in great shape.