Like everyone else says, just a hideous, hideous drop rate. Grab a pot of coffee and a good book cause you'll be here a while. This must be one of the longest, dullest grinds in the game. I had no luck at all on the shoreline, spent over an hour going all the way to the south end of the beach and back without a single drop! Decided to try the little inlet channel that runs east and north from the shore and got all 10 drops there. They came in bunches - the first two kills dropped cores, then another hour (about 25-30 kills) went by before I got any more. 3 of the next four kills dropped cores, then another 45 minutes of no drops, followed by 4 of the next 7 dropping cores. The last one took another half hour. About half the mobs drop nothing, not even cheap junk. I wouldn't mind grinding 3-1/2 hours when they're dropping 3 or 4 silver a pop, but this is just pointless. And as if that's not enough to make you quit the game for a week, then you turn it in and the quest giver asks you to do it again! Blizzard folk have a sick sense of humor sometimes. No thanks Blizz, I'll pass on the refuel quest if you don't mind.