[JSeery]

If you want to lube the spring you will need the original nut with the grease fitting. The spring bolt requires very little strength there is almost no load on it once the spring is installed. It's main function is to hold the spring together when it is not bolted in place and to center the spring when mounted. The spring lube is not grease but a special spring lubricant. Grease will make a mess out of it and plug the grooves.

Note: edited to correct, there is not a hollow bolt, it is lubed through a special nut with grooves in it.