SAN FRANCISCO (MarketWatch) -- With crude oil costs in free fall, due to worries about oversupply, the biggest beneficiaries have been consumers shelling out far less for gasoline than they were just six months ago.

However, consumers shouldn’t get too comfortable with lower prices at the pump. The amazing decline in gasoline prices has politicians eyeing state motor fuel tax increases as a way to shore up budgets and fund much-needed repairs to crumbling infrastructure like roads, bridges and tunnels.

State and federal taxes made up 20% or more of the cost of a gallon of gas in 10 states, as of Monday, based on data from the AAA and the American Petroleum Institute. That represents a rising share, given oil’s spectacular fall.

New York, California and Indiana lead with taxes making up 22% of the cost of a gallon in each state, based on Monday’s prices.

The cheaper gas has emboldened government officials to consider jacking up gas taxes.

The Federal excise tax, which hasn’t changed in nearly two decades, is 18.4 cents a gallon. Combined state excise and other taxes vary from a low of 12.4 cents a gallon in Alaska, to a high of 50.025 cents a gallon in New York, based on recent API data. The attached chart of U.S. gasoline taxes illustrates this.

Five states charge at least 40 cents a gallon: New York, California, Hawaii, Connecticut and Pennsylvania.

Nine states charge less than 20 cents a gallon, led by Alaska, 12.4 cents; New Jersey, 14.5 cents, and South Carolina, 16.75 cents, according to API data. Even Mississippi and Texas charge more.

The pressure to increase gas taxes is being felt in states like Michigan, where Gov. Rick Snyder is hoping to raise more than $1 billion through a gas-tax hike, according to a recent NPR report.

One big risk in dialing up raising gas taxes now, at least for consumers, is that oil prices eventual snap back to triple-digit levels. Then, average Americans will be doubly whacked.