Peugeot 508 Spongy Brake Pedal

Low brake fluid with a spongy pedal feel does suggest a brake issue. It could be worn brakes, as the fluid level drops as the pads wear down. Have you checked the master cylinder for any signs of leakage? When was the last time you had your brakes inspected?

I haven't checked the master cylinder closely, but I didn't see any obvious puddles. The brake inspection was probably... never, since I bought the car. If the brakes are worn, is it urgent to get it checked out?

Given the age of your Peugeot and the symptoms you described, it's highly advisable to get your brakes inspected by a professional immediately. Low fluid and a spongy pedal indicate a potential safety issue. Continuing to drive could damage other components. I advise you to take it to a workshop.

Thanks for the advice. I took it to a workshop, and you were right, the front brakes were worn. They did a fluid replacement and new pads. Cost me 480€, but at least it's sorted now.