Stores had it and it sat there. Now people are instructed properly and caught on that it was OK to use 'water' in their crankcases, and the demand went up.
Production is not the problem, a subtle shift in the store's ordering is.
Also, hurricane Ike caused a big shortage for Mobil 1 products...that is what the signs at Wal Mart are saying...as far as 5w-20, there are plenty of other brands (Valvoline, Castrol, PP) that have it in stock.
and.....when M1 does come back on the shelves watch the price fly-they've got to make up for all of these lost sales over the past few months. They will note the price increase is due to (take your pick of excuses) blah blah blah.....