In most of the cases the noise sourse is a Y motor. You can actually replace the bearings inside of it, ofc in case you at least have some experience.
Don't listen to that guys, you should NEVER apply any on a rail directly. You can add some to the inner chamber of the liner bearing but be be aware that it's pretty challenging. But also, regarding to my contacts in SKF, there is an oil inside the linear bearings that should last about 5 years at least.
How old is your printer thou? If it's 5y+, then it may will be a good idea to replace the Y motor, pulley and linear bearings as for preventive maintenance purpose.