With global crude oil prices plummeting, U.S. retail gasoline is following suit, though the bottom might not be reached until January, an analyst said.

Retail price watchdog GasBuddy.com lists Friday's average price for a gallon of regular unleaded gasoline at $3.32, down more than 10 cents from last month and 6.5 cents less than the same time last month.

Motor club AAA said it expects some retail markets could see a 20 cent drop by the end of November, provided there are no major disruptions in production.

For GasBuddy, a price drop in October is a prelude of things to come.

"We expect nationwide gasoline prices will move to between $3.10 per gallon and $3.20 per gallon in November and December," GasBuddy chief oil analyst Tom Kloza said in a Thursday statement. "The actual bottom in this current down-cycle may not occur until January."

Gasoline prices start a seasonal decline in September because the summer travel season is over and refineries start making a winter blend of gasoline, which is less expensive to produce.

GasBuddy says the futures contract for Brent crude is more than $20 per barrel below the June price. Every dollar drop in crude oil prices translates to about a 2 percent decline in gasoline prices.

The U.S. Energy Department expects the national average for a price for a gallon of gas will be $3.18 in December.