If your treadmill has a phanalic deck and started with a silicone lube in the belt you can use one.
Napa austo parts silicone 8300. your deck must be clean and not worn.
If it started with wax, You can get gulf wax and rub in on the top of the deck covering the whole surface.
It depends on your make and model.
I have a video on treadmill maintenance at www.mindbites.com/person/214-Mark
you can email me at markepeterson@austin.rr.com
Mark Peterson, February 2008