Wall Street ended an erratic quarter with a modest advance Friday as falling oil prices helped ease concerns about a weakening consumer environment in the wake of hurricanes Katrina and Rita. The major indexes finished both the week and the quarter with sturdy gains.

Stocks fluctuated throughout Friday’s session following news that personal income and spending declined last month, and that consumer confidence plunged from August.

The market was helped by the fact that crude oil eased as traders took profits following this week’s runup, but worries persisted about supply shortages this winter in the aftermath of the hurricanes.

With the third quarter drawing to a close Friday, investors acted tentatively as they prepared for the upcoming earnings season, which could indicate where the economy is headed as confidence weakens from rising gas prices and interest rates.

For the third quarter, the Dow gained 2.86 percent, the S&P climbed 3.15 percent and the Nasdaq surged 4.61 percent.