I will try to answer your problem in stages.
The operation of the oiler varies dependant on manufacturer. They usualy comprise of some form of pump either operated mechanicaly or by vacumn from the crankcase.
Oil type will affect some oiling systems and it is best to use a dedicated Saw Chain Oil which has what can be described as a 'sticky' consitancy' to help prevent it being thown off the chain.
A lack of oil usualy causes wear to the underside of the chain and the guidebar rail and may not be the only cause for a requirement to constantly resharpen the chain. When using the saw try to avoid contact with soil (usualy happens when cutting roots etc) as it is very abrasive and will dull a chain very quickliy.
Also have you checked the oiler operation with the guidebar and chain removed. If when removed you have a good flow of oil then the blockage may be in the guidebar, either in the oilway hole on the side or a build up of debris in the bottom of the chain groove. Cleanout guidebar reassemble saw and try again. Cleaning the guidebar should be performed as part of your general chainsaw maintenance.
Hope this helps
Robin S
August 2008