Agreed, no oil on the hop-up or in the barrel. Also, try not to run the cleaning cloth, patch, whatever through the hop-up itself or you may tear the rubber.
Remove your barrel grouping and look down the barrel, if there is even dust/debris a gentle wipe or two will suffice. If for whatever reason that's not enough, a drop of Windex or two.
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē