My jacks Power GEar suggest Not using WD 40---it is hard on the seal----I have used a silicone spray just before I raise them after being down for a while---or I lower them spray and retract before we leave for winter. HAve not had a dirt problem but could. They operate smoothly and have for nine years.
Check with the manufacturer about their reccomendations for lubricant on the post.
I do all my own stunts
03 Dolphin LX 6355, Workhorse W22, 8.1 vortec, 04 CR-V, Blue Ox, Brake Pro----Norm, Barb and
Doc(He's a PhD)