Saudi Arabia's plan to boost oil output by 500,000 barrels a day is likely to lead to cheaper crude and a slight easing in the prices consumers pay for gasoline and heating oil, energy analysts said yesterday. The world's No. 1 oil producer decided to boost production after it became clear that an increase agreed by Organization of the Petroleum Exporting Countries (OPEC) oil ministers last month was not enough to trim prices from levels in excess of $30 a barrel.