Why are gas prices rising? If oil prices go up, gasoline prices at the pump follow -- though if oil prices come down, gas prices don't necessarily drop. Crude oil prices have been climbing to new heights recently.

Recently crude futures reached an all-time record of $103.95 a barrel before closing slightly lower. The prior record, set in April 1980, was $103.76 when adjusted for inflation. A barrel cost less than $25 on Sept. 11, 2001, as measured in 2006 dollars.

What might drive prices up to and over $4?

• Continued oil-price increases.
• Increased demand as more drivers return to the roads in the warm weather.
• A pause in supply as refineries make their annual changeover from winter-formula to summer-formula gasoline.

Nationwide, the average pump price for regular gasoline rose 3.2 cents to $3.162 a gallon in the week ended Monday, the government said. The price was 65.7 cents per gallon higher than a year ago, the U.S. Energy Department said in a weekly report. Diesel fuel rose 10.6 cents to $3.658 a gallon, according to the report, which is based on a survey of about 800 filling stations. The price of gas rose the most in California: up 13.1 cents to $3.459 a gallon. California had the highest average price. The lowest average price, $3.08 a gallon, was in the Midwest region, where prices were unchanged from last week.