Before someone shouts you out for a post they should be in the technical section. I'll give you my two bobs worth.

The bearings on the slides are sealed for life and unless they are damaged do not need greasing. The slides are a different matter.

Using any grease can and will collect sand and grit. It can build up and cause the bearings to stop rotating. I used to own a Mazda E200 with the sliding door. I always cleaned the slides with degreaser and wiped it after with a dry cloth then rubbed a candle along the tracks. It didn't seem to pick up as much grit as Silicone spray WD40 or other grease products.

I cannot remember the name of it but there is a stick of some stuff that also lubricates the tracks without greasy build up. Goss dry lubricant I think

There is another option Dry Teflon. It's actually designed for Motorbike chains to lubricate them and resist sand and grit so ideal for the slide tracks.

This is a link to the Teflon product

http://www.wiggle.com.au/finish-line-dry-teflon-lubricant-120ml-bottle/?lang=au&curr=AUD&dest=27&sku=4000000074&utm_source=bing&utm_term=&utm_campaign=AU_Shopping_Low-Margin&utm_medium=base&utm_content=mkwid|p3BhhS0O_dc|pcrid|74835583946521|pkw||pmt|be|&pgrid=1197368497264311&ptaid=pla-4578435151316367

I'm sure someone will come up with  more advice and solutions .

Hi 

I have had quite a few sliding doors. Do not grease them as it will just attract the dirt. I usually just spray them with WD or similar and keep the tracks clean and the dirt out of the  bottom track. Possibly a dry lube spray would be better but I always have some WD in the van so it is good for lots of things that need a bit of instant lube.

Jaahn