Gas prices in the U.S. have remained steady despite a drop in the cost of crude oil.

Despite new downward pressure on the price of crude oil on global markets, the price of gasoline remained unchanged across the U.S. and prices in California actually increased substantially, according to a survey by AAA.

The national average price for regular unleaded gasoline is $2.77 per gallon this week. The average is just fractions of a penny more than a week ago and is at the lowest mark for this date in nearly five years.

The steady national average obscures price variations in several states including California, where prices increased by 28 cents per gallon, and the decline in prices around the Great Lakes as prices in Indiana and Michigan fell by more than 10 cents per gallon.

Over the last month, motorists in Indiana, Michigan, Ohio and Illinois have seen the biggest drop in prices as refinery issues that reduced supply temporarily have been addressed.

Despite strong for gasoline across the country, AAA reported the average retail price for gasoline has fallen for 19 of the past 30 days and is three cents per gallon less than the 2015 peak price of $2.80 per gallon, which was reached in June. Many consumers continue to save at the pump with national prices down three cents per gallon month-over-month, and yearly comparisons show the full extent of savings with an 85-cent per gallon discount.

Drivers in California are once again weathering sharp increases in gas prices due to reports of tightening supply in the state. The state average has climbed by 22 cents per gallon since Friday and drawn the attention of the California Energy Commission, which is now investigating the fundamentals behind this most recent spike, according to AAA.

Preliminary reports from California indicate that the despite refineries exceeding last year’s production rates, higher than expected demand for gasoline has resulted in significant drawdowns in supply and distribution systems have been unable to keep pace.

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On the heels of this price surge, California, at $3.72 per gallon, is once again the nation’s most expensive market for retail gasoline. The state is followed by regional neighbors: Alaska, at $3.47, Hawaii at $3.34, Nevada at $3.25 and Washington at $3.20 as the top five most expensive markets for retail gasoline. South Carolina at $2.41 per gallon and Mississippi at $2.46 have the cheapest gasoline.

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While a handful of states have seen prices rising and falling sharply, pump prices have been relatively stable across much of the country over the past seven days, moving by 2 cents up or down in 42 states and Washington, D.C. Averages are down in 30 states week-over-week, with prices in Indiana and Michigan reflecting the only double-digit savings. Drivers in 20 states and Washington D.C. have seen prices climb higher during the same period.

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Domestic supply factors continue to influence gas prices in some states. However, lower global crude oil prices are contributing downward pressure on gasoline prices. The impact of the Greek debt crisis and diplomatic negotiations with Iran pushed the price of West Texas Intermediate crude oil to multi-month lows over the past week. Greece’s default on its International Monetary Fund loans has fueled concerns regarding the impact on other Eurozone economies.