I contimpated putting this on the Mechanics forum, but am posting it here in fear of being laughed out of the forum.

I have a 20-30 year old 'comfort' bike with a Brooks/Schwinn/Raleigh/whatever seat with the two big springs under the pelvis and the longer springs under the pleather fore to aft. It squeaks loadly when I pedal. Having bathed it in WD-40, nothing has changed. Is this fixable (without replacing the seat)?

Try putting some thick grease in between the springs. It could be squeaking from the steel springs or where the springs attach with a bolt to the underside of the seat. I have heard and seen this before.

my seat squeals like a rat too. I identified the source as being the pleather rubbing and stretching against the metal form underneath. I tried grease on the pleather and metal to no avail. but if it's the springs...

+1, it's not the spring itself, it's generally where the spring attaches. Put a wedge in a spot, ride it, and then keep trying different places until you notice a difference. Eventually, you'll find the area, and can kill it dead, often just by moving the spring/metal a bit, a little grease or graphite lube, and let it relax back.

dang, i was gona suggest wd-40, it worked when i had a squeky seat

I have a couple of those old mattress seats that have a squeak emanating from the hinge under the nose. I suppose if I wanted to quiet them I would grease that hinge point.