Motorists are expected to see another round of rollback in the pump prices of petroleum products this week.Based on industry estimates, diesel may generally drop by P1.80 to P2 per liter.Gasoline prices, meanwhile, may be reduced between P0.30 and P0.60 per liter.In its fuel forecast for August 16-22, Unioil Philippines said diesel could go down by P1 to P1.20 per liter; gasoline should have no price change to a rollback of P0.10 per liter.Oil companies usually announce price adjustments every Monday, to be implemented on the following day.Effective last Aug. 9, Tuesday, fuel firms slashed pump prices of gasoline by P2.10 per liter and diesel by P2.20 per liter, bringing the year-to-date adjustments to stand at a net increase of P17.55 per liter for gasoline and P30.15 per liter for diesel.