Gas prices at the pump across the U.S. are up 20 percent from last month, according to USA Today. While many people may blame this on the situation in the Middle East, analysts say there are other causes.Major among these is the complicated switch by refiners from winter-blend fuel to summer-blend fuel, required by air quality regulations. The blends differ in various parts of the country, so refiners are usually limited to supplying just one area. A regular seasonal summer rise in crude-oil prices, plus a strike in Venezuela that is keeping crude oil off tankers, are also partly to blame.Experts think the national average price should peak at $1.60 per gallon, perhaps as early as next month. Before the Iraqis embargoed their fuel exports, those same experts were predicting the peak at $1.46 per gallon. The authors say that this is like finding out that the SUV you want is now $30,000 instead of $25,000, or that the suit you were planning to buy is now $600 instead of $500.