Find Grek and ask him to try it on his weapon. Once he's tried out the oil, return to Rakoria with the results.
The oil is finally ready for its first test. It seems heavy enough to serve as a high quality weapon oil.
The only way to find out is to have a professional try it out. See Grek over there by the wanted posters? Sure, he's no poet, but the orc knows his way around a weapon!
Take a sample of the oil to him and ask him to use it on his weapon. After he's had a chance to test it out, let me know what he thinks of it.