2005 Nissan Altima • 100,202 miles

I have a 2005 Nissan Altima 3.5SE. The Manual says the gas tank capacity is 20 GALLONS. When the gas light refuel yellow light turns on I fill up my tank at the small line right above E. I filled up 13.702 gallons and it went past full. How is this possible for 20 Gallons if 13.702 gallons goes past full? Also does winter time with temperatures of 5-20 degrees decrease gas mileage? I'm only gettig 15.5 city.
February 21, 2013.

When the low fuel indicator light comes on, there is still a lot of fuel in reserve and tank is not dry so 14 gallons is correct though it could be slightly be less than expected to be filled.

Cold weather would definitely reduce gas mileage as a richer running condition is required but it should not go off the chart from normal.

May 5, 2013.