With heating oil prices topping $5 per gallon, an all-time record in New England, people who depend on the energy source to stay warm are getting walloped in the final weeks of winter. In the Northeast, a snowstorm this weekend is expected to bring more than a foot of snow to parts of the region, proving that the cold weather isn’t ready to relinquish its grip. One energy expert encouraged New Englanders to purchase only what’s needed until warmer weather arrives. “There’s no need to fill up your tank. The best advice is to buy just what you need because prices will be coming down. This is a spike and prices will be coming down,” said Mark Wolfe from the National Energy Assistance Directors’ Association.