Gate Rollers - Lubrication

or you can replace the metal rollers by the plastic ones as on the picture ,no lubrication needed what so ever...

Just to clarify - when I say rollers, I am referring to the wheels.

Perhaps I should have made that clearer in my OP.

when the wheels are not rolling good , replace them , you have 2 different , the best ones are those with closed bearings and normally no need of lubrication..., the ones with open bearing you can lubricate but even than they do not last long..
and the wheels are inexpensive , 120-165-195 baht depending the size ( 2,5 or 3 inch...)
the lubrication with what ever spray will not last long..so is only good as temporary solution....