"If it goes down 40 cents, and stays there it would be worth about three- to four-tenths of a point on GDP," he said.
Lipow said he does not expect gasoline to stay at its lows for long, but it could see a rather quick drop with falling oil prices in the next several weeks. The real benefit to the U.S. economy would come if lower prices could be sustained.
Tom Kloza, chief oil analyst with GasBuddy.com, said he sees gasoline prices bottoming between the middle of October and middle of December.
"I think we'll see a number of states where people could see close to $3. Our informal projections are that the nationwide average will bottom close to $3.15, $3.20," he said. "One thing that could happen...which probably pushes the U.S. below $3.40 this weekend is that in corn, there's a complete collapse going on."
Kloza said corn-based ethanol was trading at about $1.80 in Chicago Thursday and appears headed for a multi-year low. "Ethanol continues to fetch a price that's 60, or 70, or 80 cents under gasoline," he said adding that U.S. gasoline typically contains 10 percent ethanol. The USDA Thursday forecast a record corn crop
Read MoreChoking on oversupply, oil could fall another 10 percent
The outlook for oil is bearish with the market more negatively tilted toward Brent than West Texas Intermediate. Brent crude, the international benchmark, sunk below $99 per barrel Thursday, while WTI, representing U.S. light sweet crude, edged higher to $92.83, after touching a low near $90.
"If we see continued weakness in oil prices that could bring gasoline down towards $3 a gallon, and this would be a stimulus for the economy," said IHS Vice Chairman Daniel Yergin.
Economists are already assessing the impact of lower gasoline prices on consumption and inflation in the U.S.
"I would say from a global growth perspective, the risk is tilted in that direction toward continued concerns about global growth, and if WTI would continue trending lower that's something that, on balance, would help the U.S.," said Barclays economist Michael Gapen.
He said a 40-cent change in prices at the pump would have a small impact on the economy, and it would show up as a minor impact in headline consumer price inflation. "In terms of oil and gas and the effect of energy prices on consumer behavior, it's more about the speed of change than the absolute level of change," Gapen said. For instance, "If there's a very sharp rise in the price of oil in such that the price rises sharply in a several month period, it's hard for households to get out of the way of that."
Some analysts expect WTI to reach $85 per barrel—and possibly lower. At $85 for crude, gasoline could hit $3. The stronger dollar, an Atlantic basin supply glut and weaker global growth—especially in Europe—are combining to create a headwind for crude, and a positive for consumers. But that is negative for producers, who could cut back on production to steady prices.
Read MoreCrude conundrum: When - and if - output cuts will come
The International Energy Agency on Thursday cut its forecast for world oil demand for both 2014 and 2015 in its monthly report. "The recent slowdown in demand growth is nothing short of remarkable," the IEA wrote. It said 2014 demand growth should now be 900,000 barrels per day, off by 65,000 barrels per day from its earlier forecast, and it trimmed 100,000 barrels from 2015 growth to 1.2 million barrels per day.
IEA cut its forecast for China oil demand growth in 2014 from 2.9 percent to 2.4 percent. China demand projections were cut by 100,000 barrels a day for 2015 to 10.6 million a day.
"China chill has settled over the oil market," said Yergin. "These are quite low numbers for Chinese demand. It's recognition that demand is weak, and what does that tell you about the real state of the Chinese and world economies?"
The IEA expects non-OPEC supply to grow by 1.6 million barrels per day in 2014, and by 1.3 million barrels per day in 2015. It lowered its forecast for demand for OPEC oil for 2015 to 29.6 million barrels per day, compared with recent levels of 30.3 million barrels per day.
Saudi Arabia in August already trimmed its production by 400,000 barrels and is now expected to be less than 10 million barrels a day. Analysts anticipate further cuts by the country, if prices fall much further.
Read MoreOil demand growth slowing at 'remarkable' pace - IEA
The U.S. is adding to world oil supplies at a rapid rate. "In the U.S., from 2013 to 2014, our production increased a million barrels a day," Lipow said.
Including Canada, increases in North American production have been able to cover global demand growth from 2013 to 2015.
"The U.S., by itself, has increased its production of oil enough to meet the entire world's increased demand for 2014, and in 2015, the IEA is now predicting world demand would go up by 1.2 million barrels a day, and the U.S. EA has now increased its U.S. production forecast from 2014 to 2015 by 1 million barrels a day," he said.
Weakening economic data in Europe and the drop in demand from European refineries are negatives for oil prices.
"The latest thing that brought some negative pressure on oil prices was the (August U.S.) nonfarm payrolls, which was really disappointing. I think it's feeding on negative sentiment," said Gene McGillian, energy analyst with Tradition Energy. "I think the market has priced in a lot of the poor, negative outlook. We're still in the process of finding a bottom. We've come off considerably considering we have all these (global hot spot) problem areas."
The threat of ISIS in Iraq, and the tensions between Russia and Ukraine are acting as support for oil prices, but analysts say they are not big factors as supplies are not now expected to be impacted. The return of some Libyan oil to market is also adding to the supply glut in the North Sea and Atlantic basin.
Watch this: Oil market in bearish trend
U.S. refineries were at more than 93.5 percent capacity last week, according to government data, but that could change quickly as refineries go into maintenance after the summer driving season. That would result in more than a million barrels a day reduction in oil demand temporarily, said Lipow.
"This needs to be watched carefully. About 1 million barrels per day of U.S. refining capacity will be offline for maintenance, with the peak of the maintenance cycle around early October. That can make U.S.crude values very sloppy, even though $90 bbl or higher seems to be a reasonable price for the next few years," said Kloza. He does not expect the low crude prices others are expecting.
The U.S. produced 8.6 million barrels of crude a day last week. "Based on what the EIA is saying, where they increased the production forecast to average 9.5 million barrels in 2015, I feel by the end of 2015 U.S. oil production could actually reach 10 million barrels a day, which would be the highest level since 1970," Lipow said.