Retail gasoline prices have risen nearly 5 cents in the past two weeks and could increase even more as retailers see their profit margins tighten, Reuters reported.

The national average for self-serve regular unleaded gas was nearly $2.80 a gallon on Oct. 19, up 4.92 cents per gallon from two weeks ago, according to a Lundberg survey of about 7,000 gas stations. Prices were about 38 cents less than the all-time high of $3.18 on May 18, 2007.

However, with crude oil prices up the equivalent of 18 cents per gallon, survey editor Trilby Lundberg expects retailers to increase prices to make up the difference. Demand for winter heating oil will also be a factor. Lundberg expects prices of that fuel to exceed $3 per gallon in the coming weeks.

The Associated Press reported this morning that crude prices have jumped 28 percent since late August, driven by a weak dollar, low supplies at a key oil terminal in the Midwest and worries over tensions between Turkey and Kurdish rebels in northern Iraq.