The question facing investors, companies and policymakers is how low oil prices will go ?" and for how long. Every day, American motorists are saving $630 million on gasoline compared with what they paid at June prices, and they would get a $230 billion windfall if prices were to stay this low for a year. The vast majority of that will flow into the economy, with lower-income households living on tight budgets likely to use money not otherwise spent on gas to buy groceries, clothing and other staples.