And some people think it's a bargain. . .

The pumps read 99.9 cents a gallon.

That, more than volumes of words, sums up the world-wide oil glut - at least in the town of Vineland, N.J., 25 miles south of here.

Two Sunoco gasoline stations in Vineland, Rich's Sunoco and Gear Automotive Service, are selling gasoline for 99.9 cents a gallon. They join a number of other stations around the country that have gone below the $1 mark.

These under-a-dollar prices to some extent reflect the unprecented plunge in gasoline prices in the past two weeks. Los Angeles-based oil industry analyst Daniel Lundberg calls this drop ''the sharpest national decline for any two-week period in history.'' He attributes it to the global oil glut and changes in driving habits, including greater use of fuel-efficient small cars.

Will the decline continue, even in the wake of OPEC's new plan, recently announced, to cut oil production and stabilize oil prices?

Over the weekend, US Energy Secretary James B. Edwards said he thinks so, at least for the next several months.

According to Mr. Lundberg's calculation's, the average price of gasoline has dropped 12 cents in the past 16 months. Lundberg now pegs the average price of retail gasoline, including all taxes, at $1.216 a gallon. The American Automobile Association reports that prices are down an average of more than 5 cents since last April, with new lower prices expected shortly.

But it should be noted that such national figures are often undercut - and sometimes exceeded - by what's happening locally. This is the case in Vineland, where the Sun Oil Company's extensive rebate program is coupled with intense local competition.

Robert A. Dietshe, a Sun Oil Company spokesman here, says the company is offering rebates to gas dealers whose sales are more than 75 percent of the gasoline they sold last year during the same month.

Carl Senseman, manager of Gear Automotive Service, says business has quadrupeled since he recently lowered his price of regular gasoline.

But is he making money? ''No, not in the short range,'' he says. ''Our profit will be at the end of the month when we get our rebates back from the oil company.''