The average price of a gallon of self-serve regular gasoline in San Diego County rose Friday to its highest point since Oct. 24, 2008 because of recent increases in the price of crude oil.A increase of seven-tenths of a cent pushed the average price to $3.162, 3.8 cents more than a week ago, 5.6 cents more than a month ago and 79.1 cents more than this time last year, according to figures from the AAA and Oil Price Information Service.The average price has risen seven of the past eight days, including eight-tenths of a cent Wednesday."Gas prices have so far been following the slow march of oil prices on the way up," Jeffrey Spring of the Automobile Club of Southern California said."It's kind of surprising it has not gone up farther and faster, what we typically see in the spring. The fact that the number of miles driven continues to drop is holding back further increases."Crude oil costs account for two-thirds to three-quarters of the price of a gallon of gasoline, according to Tupper Hull, vice president of strategic communications of the Western States Petroleum Association, a trade association representing major oil companies in six Western states.Oil prices increased "because they've been a hedge for investors against the value of the dollar," Spring said."It has nothing to do with the supply and demand of the product itself," Spring said. "It's being treated as a pure commodity trade for a lot of people. Oil typically holds its value better in times when the dollar is not doing so well against other currencies."The oil spill in the Gulf of Mexico is not affecting Southern California gasoline prices because the region gets little oil from the Gulf of Mexico, getting the bulk of its oil from California, Alaska and overseas, Spring said.