First of all, “sliding doors” don’t slide! And therefore, don’t need grease. They Actually Roll ! Built into the bottom frame of the door, there are two to four wheel assemblies with ball bearings, called “rollers”. There are over 300 different combinations of roller material, designs, sizes and styles for the various sliding doors that have been manufactured over the last fifty years. The ball bearings in the center of each wheel last longer when lubricated with dry Teflon. (This dry lubricant will not attract dirt, hair and fur or get gummy with age.)
IT IS NEVER ADVISABLE TO LUBRICATE, GREASE OR WAX A TRACK.
If the sliding door no longer moves with ease, it’s time to just clean everything and replace the rollers.
It’s a shame there are professional appearing people telling you to grease the track, recommending lubricants and waxes for the job.