Tumult in international markets raises large questions about oil demand in the next couple of years. Inevitably, answers depend on performance of the global economy, which at this point is impossible to predict. August 2011 has been a wild month. The US Congress barely met an Aug. 2 deadline for the budget deal it needed for political reasons before it could lift the government's debt ceiling. The Department of the Treasury had warned that without new borrowing it wouldn't be able to meet all obligations. Fear spread that default would result in an historic lowering of the government's premier credit rating. On Aug. 5, one of three major credit judges, Standard and Poor's, lowered its US ...