I took the relief valve apart, cleaned it and that seemed to solve the issue. Thank you all!

Great, I certainly will also do it! Thanks again

Huib, thank you very much for your very helpful reply. I'll then see if cleaning the sender contacts helps.

I've just removed the relief valve and it was stuck in the open position. Shouldn't it be closed? Anyway, I took it apart, cleaned it and didn't see any damage. Could this have been the problem of the low pressure?

Neil, thanks for your reply! I did check the wire on the oil sender and the dipstick and everything was ok.

Mijn Fulvia S2 maakt een 'metaalachtig' geluid achter wanneer ik maar ietjes te snel over een hobbel rijd (alsof een metaalonderdeel het carrosserie rechts in de kofferbak raakt). Wat zou het kunnen zijn?.. Alvast bedankt.

I changed the oil in my S2 and made a 300 kilometre round trip. On the outward journey the oil pressure was ‘normal’, usually between 35 and 70. On the return journey I noticed that the pressure didn't even reach 35, including at 100 km/h and 3.500 RPM (photo). The engine runs beautifully. Any ideas...

Good idea!...

Thank you very much Huib... spot on! I changed the fuel filter, cleaned the fuel pump, inspected the tank, new air filter...and... back on track!

Thanks very much Huib. I'll have a look within a few days.