Drivers around the U.S. have seen some modest relief at the pump lately as gasoline prices retreat toward $4 a gallon. But motorists shouldn't bank on fuel costs returning to where they were just before the Iran war anytime soon, according to experts. Mark Zandi, chief economist at   Moody's Analytics, doesn't expect gas prices to drop below $3 this year absent a major economic shock, such as a recession.  "Under the most optimistic scenarios, I would expect gas prices to settle closer to $3.50