I just got my first folder 
It's a stainless steel opinel #8
and I like it a lot 
And my brother have got a #2 for his keychain , but it's so stiff to open , do you have any solutions for that ??
Good Choise. The No8 is a classic knife
The No2 has to be a bit tight as it has no lock or spring to keep it open.
If it was not tight it would not stay open or shut.
Sometimes opinels get wet and become very tight, so if you dry them a bit they loosen up.
However if it is too tight then there is a problem.
Using it a lot will make it loosen up a bit.
Using standard oil will not work at making it loose, as it will soak the wood and make it swell and more tight
Usually with opinels I go to the shop and try lots of them untill I find one that feels right.