There are no gasoline lines at Mary Dilworth's Amoco station in Rockville, but she's noticed a "buildup" of cars at the pumps the past few days.

"The cars, we can't keep 'em filled she said yesterday. "A lot of 'em are beginning to top off. People come in and say they heard on TV "that there may be gasoline lines again in October."

Is it possible?

According to interviews yesterday with oil company executives, local energy officials and other observers, the short answer is maybe.

"It's important to reiterate that the $ supply situation has not improved so greatly that we can forget about the risk of lines returning," said the District of Columbia energy chief, Chuck Clinton.

This October, the 1,500 service stations in the Washington area will pump 86 to 94 percent of the gasoline that they pumped in October a year ago, according to an analysis by The Washington Post of oil company statistics.

The metropolitan area endured seven weeks of gasoline lines last summer. During that time, stations in the area were generally pumping 75 percent or less of year-earlier volumes.

In June local jurisdictions imposed an odd-even-day gasoline purchase plan that was credited with helping to cut the lines. That plan was lifted Oct. 1, but minimum purchase requirements to discourage "topping off" of gasoline tanks remain in effect.

What apparently triggered the current concern among Dilworth's customers and others were television news reports about a recent issue of the authoritative gasoline marketing publication, "The Lundberg Letter."

"Gasoline Shortage Worsens," warns its Oct. 5 headline.

The publication examines the extent to which gasoline supplies for a given month this year fail to meet the consumer demand for gasoline during that same month last year -- when supplies were plentiful and demand was unrestrained. Lundberg's analysis shows this supply-demand shortfall during the last few months: May -- 12.8 percent. June -- 11.2 percent. July -- 10.6 percent. August -- 10.2 percent. September -- 7.1 percent. October (projected) -- 10.6 percent.

"Gasoline supplies will be significantly tighter in October than they were in September, reverting to conditions of two or three months ago," the publication concludes from the statistics. "This raises the possibility of long waiting lines at service stations in some [cities] . . ."

The publication explains that while the oil companies aren't cutting back on supplies this month, October is traditionally a heavy-driving month, with a bigger demand.

That's what may throw the delicate balance of supply and demand out of whack in October, the publication says.

But oil company representatives yesterday attacked this analysis. They said that Americans have changed their driving habits and are driving less, so there probably won't be a big surge of driving this month the way there was last October.

"We don't see any cause for alarm over the short term. We see no lines in October," said Gulf spokesman Kirk Vogeley.

"If something should happen to worldwide crude oil supplies, then certainly there coulb be some problems down the road," said an Amoco spokesman.

"Personally, I think Lundberg is blowing smoke," said Shell Oil spokesman John Houser. "he's probably going to be selling more of his Lundberg Letters."

The recent edition of the letter was a hot item among energy officials yesterday.

"I've got it right here on my desk," said Virginia's fuel allocation manager, William E. Kirkland. "I just honestly can't say that it's germane in Virginia."

Exxon spokesman Chapin Burks summed up his company's position this way: "Exxon expects supplies of gasoline to be tight but manageable during the coming winter and spring. Providing that consumers continue their conservation practices . . . and there is not a reduction of supplies of crude oil, then there should be no lines) $. The lines could reappear if either of these circumstances change."

Jonathan White, a spokesman for the American Automobile Association, said that the lifting of the odd-even rules on Oct. 1 was "premature." He said the rules were good because they "made people think twice" before filling their tanks.

"If gas lines do come back, we know how to deal with them," said White.

Local energy officials said they used their special powers under federal rules to direct hundreds of thousands of extra gallons of gasoline to the Washington area for the pope's visit last weekend.

When smaller-than-expected crowds turned up to see the pontiff the extra supply went unused over the weekend. However, it remained in the Washington area and is now being sold by the stations to which it was delivered.

In all, that extra supply will add about 1 or 2 percent to the volume of gasoline available in the Washington area this month.

Ralph M. Presutti, a Camp Springs Shell dealer, said yesterday he thinks Lundberg's analysis may be "triggering problems."

But Presutti said his customers -- apparently unlike some of Dilworth's customers in Rockville -- are not showing any signs of concern about gasoline supplies.

Only about 60 percent of his customers say, "Fill it up," according to Presutti, and that's about normal. During last summer's gasoline lines, he said, everbody wanted their tanks filled to the top.