The waning days of summer should mean the last increases in gasoline prices for a while.
Average gasoline prices rose 1.5 cents overnight to $3.843 per gallon Tuesday, the biggest gain in two weeks. The price has risen about 50 cents since July 1.
Motorists in about eight states are paying at least $4 per gallon, according to AAA, Wright Express and the Oil Price Information Service. Even the lowest prices — $3.59 in Mississippi and $3.60 in South Carolina — are up more than 60 cents from early in the summer.
Yet, relief is in sight. Refiners can soon switch to selling winter blends of gasoline, which are cheaper than summer gasoline blends formulated to reduce pollution.
"This is the fireworks finale for the season, the next four or five days," said Tom Kloza, OPIS chief oil analyst. "By next week, it will, it will start to move lower."
This week, short supplies of summer gasoline, particularly in the Northeast, are contributing to the latest increase, Kloza said. He also said cited lingering effects from supply disruptions caused by Hurricane Isaac and refinery downtime in the Midwest.
The national average for gas is within a dime of the year's high, so a decline will be welcomed by drivers. Gas prices topped out at $3.94 per gallon in early April, then fell for about three months. But rising oil prices, pipeline and refinery issues and the vacation driving season pushed prices up 10 percent since the start of summer.
Overall, the national average price has increased 3.2 percent so far this year, compared with the same time period in 2011, according to OPIS data. Just one state — Montana — has seen lower prices year to date, although by just 0.1 percentage point. In Arizona, the average price is up 6.2 percent from a year ago.
Meanwhile, oil prices rose slightly ahead of a meeting this week where the Federal Reserve may decide to take additional steps to promote economic growth. Such measures can mean more demand for oil and other energy products.
Traders also are awaiting a decision from Germany's high court, expected Wednesday, on whether the country can participate in a European bailout fund.
Benchmark oil rose 63 cents to finish at $97.17 per barrel in New York. Brent crude, which is used to price international varieties of oil, gained 59 cents to $115.40 per barrel.
Other futures prices on the New York Mercantile Exchange:
— Heating oil rose 1.89 cents to end at $3.1857 per gallon.
— Wholesale gasoline gained 1.95 cents to end at $3.0435 per gallon.
— Natural gas increased 18 cents, or 6.4 percent, to end at $2.992 per 1,000 cubic feet.