john hamilton wrote:

The hinges on our Fujitsu laptop screen appear to be 'all' plastic and they get very 'difficult to move' making the
screen difficult to fold up and down.

We have have tried 'WD-40', but that seems effective for only a very short time.

And is bad for the plastic.

We are afraid to use ordinary oil as we thought it might effect the plastic.

So does WD-40.

We were thinking of using olive oil, but somebody has told
us that olive oil 'degrades' and goes sticky, over time.

Correct.

We have got some Camellia oil that was given to us, and it's made from
Camellias and it comes from Japan and is suppose not to 'degrade'.
Still it's an unknown quantity to us.

Bad for the plastic too.

Does anyone know what would be a suitable and safe lubricant in this case?

Silicone oil.

Since we dont want to cause any problems with the plastic on this lap top.

Yep, if you degrade the plastic, it will break.