How do I unplug the bar oiling system on my Homelight chainsaw?

I mixed a couple of brands of bar oil. This evidently caused the bar oil filter/screen and pump to clog and not pump any more oil. What kind of oil thinner or other liquid product can I put in the bar oil reservoir to thin out the bar oil so it will pump? The oil reservoir is a plastic container so the thinner has to not attack the reservoir. This is a Homelite 42 cc saw.