By Jim Williams

(CBS) — Gas prices continue to drift lower. reports they dropped seven cents in Chicago in the past week.

The lowest price: $1.79 at Costco in Bolingbrook. You can find it for $1.72 at some stations in Gary.

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That trend is a big boost for the bottom lines for many companies and cities.

CBS 2’s Jim Williams reports months ago governments they didn’t anticipate today’s plunging oil prices, so now they have extra money. But one analyst warns: don’t be so quick to spend it on other things.

Evanston is one of Chicago’s largest suburbs, with 300 city-owned vehicles, fire trucks, plows, police cars, garbage trucks and it takes a lot of money to fill their gas tanks.

“Our budget is about 1.1 million and we’re running about 55 percent so if this holds up we could save about a half million dollars easily,” said public works director Suzette Robinson.

All that savings because gas is a lot cheaper than it was when governments put together their budgets. It’s a windfall for government agencies in Chicago, too.

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“Most of them are looking at their budgets and saying ‘Where did this money come from?” said Fox Business news analyst Phil Flynn.

Flynn says the temptation might be for governments to spend the savings on other things they need. For instance, Evanston could use new garbage trucks and an ambulance.

But Flynn warns gas prices are volatile, and could jump again.

“They ought to save the money for a rainy day,” he said. “Who know if we’re going to have a huge snow storm in February or March? We may need that money later for snow removal or more salt…I warn most municipalities to not spend the bonus just yet.”

Still, a “bonus” that’s welcome in governments everywhere.

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You be wondering if oil prices are dropping why are airfares the same? CBS 2 contacted several airlines and they told us they’ll be releasing information on their fuel costs in the next few weeks.