When it comes to gearbox maintenance, one of the most important elements is proper lubrication. Not only does the lubricant help protect the gear teeth from friction damage, it also helps to draw heat out of the gears as they work. In most gearboxes, the lubricant is also key to protecting the bearings in the gears. To get the most from your gearbox, you need to use the right lubricant. Here are your three primary options.