top 5 reasons for fusel oils

[brewster]

i have now done my 1st 5 runs and can not seem to get rid of the bad taste in my vodka ...i assume it is being caused by fusel oils....i have asked a million questions and have read tons of stuff regarding oil, but can not get rid of it....i am using a reflux still, 48 hr. turbo yeast with a sugar wash (7 kg sugar)i do not add the yeast until i know the temp is right....i ferment until my hydrometer says its ready then let stand and clear to a very light color yellow(6 to 10 days)...i do a quick run and then the second run i do at 78c...i collect in small mason jars but all the jars from the 1st to the last have oil film that i can see when held up to the light....i am using a copper packing from brewhaus...i filter through a column that i also purchased from brewhaus....i fill the column with activated carbon(tap the column so its fairly tight) run water in it and b4 the water leaves the funnel i put in my product and then water on top of the product just b4 it leaves the funnel...but still have the bad taste after filtered....i am completely lost as to what in the hell to try next....can someone out there please give me some ideals what i might be doing wrong...would distilling 2,3 or 4 times help ??? what are the top 5 reasons you get oil ????????????? help, help help