Ok so I was driving for 20minutes and then stopped for fuel, then after another 20 minutes of driving the oil light came on when idling and went off when driving. I travelled for about 50 miles with it like this, then I stopped and left the car off for about an hour and a half and the light doesn't come on anymore.

Any ideas? Should I just monitor it or is it worth investigating? Does the Felicia (1999 1.3 Glxi) have an adjustable pressure relief valve?

Cheers

When did you last change the oil? The light is a low pressure light and if the oil gets old and thin the pressure falls and it will come on, either that or if there is too little oil in there. Other possibles include worn bottom end bearings or oil pump (expensive and scary unless you can DIY).....but with your symptoms I think an oil change would sort it.

Oil was changed recently, only done 900 miles since. Oil level is ok too. Don't understand how it can happen on one journey and then be fixed after the engine was off for a while, makes me think it could be an electrical fault?

You could try changing the sender, but if it comes on after a decent drive everytime then its more than that. What grade oil did you use? How many miles has the engine done? Could be the bearings starting to go if its not the oil.

Using 10W40 in it and it's coming up to 65k miles

That should work fine and the bearings shouldnt be going at 65k....check the sender, but it does sound like its mechanical/oil. If it was mine, I would try changing the oil first.

what oil filter do you have, I would only fit a Fram or Coopers filter (Z27A).

the oil get thinner as it warms up but I would make sure the filter is the right one and maybe change the sender switch.

The Favorit I had over the summer did this and an oil and filter change sorted it. The previous owner said it had done less than 30 miles on the oil in the engine....but it had been sat for a year. If it was the sender it would be faulty all the time.

Oil was changed recently, only done 900 miles since. Oil level is ok too. Don't understand how it can happen on one journey and then be fixed after the engine was off for a while, makes me think it could be an electrical fault?

You could try changing the sender, but if it comes on after a decent drive everytime then its more than that. What grade oil did you use? How many miles has the engine done? Could be the bearings starting to go if its not the oil.

I had this before, in almost exactly these circumstances. Long story short, a speck of carbon got loosened by the oil change, and found its way into the capillary for the pressure sensor. I'd check the electrical connector there, and if it's ok, change the sensor before doing anything else.