I don't know a ton about the 028, but I don't think I've seen one that had an adjustable oiler. However, mediaCAT shows two different pump pistons - one with a .6mm stroke and one with a .7mm stroke, so I suppose any given oiler (depending on sub-model & vintage) could have a different output. Are you looking to increase the output of yours? If so, mdavlee has a thread on here about modding the internal components to accomplish that.