Every rule of government budgeting — not to mention common sense — says using a one-time windfall to finance ongoing commitments is a very bad idea.

It’s the political equivalent of hitting the lottery for $1,000, then rushing to put a down payment on a Ferrari.

So it was disturbing that Gov. Cuomo — when asked how he would spend an unprecedented $4.2 billion in legal settlements flowing into state coffers this year — threw out the following list of options:

“We could do more infrastructure, we could do more to invest in education and we could do more to cut taxes.”

Sorry, gov, but two of those things are not like the others.

Investing the influx into infrastructure — that is, roads, bridges and other capital projects that cost a lot up front while providing benefits for decades to come — is sound practice. So is using the money to retire some of the state’s $56 billion in long-term debt.

But using temporary money to permanently boost education spending or cut taxes is exactly the kind of thing that Cuomo, normally a voice of fiscal sanity, should be ruling out.

Certainly, residents of the highest-taxed state in the nation deserve relief. And schools in New York City and other struggling districts could use extra money.

But those commitments would only be real if backed up by stable, long-term sources of revenue — which the settlement money definitely is not.

It’s not every year that New York is set to collect $3.6 billion as its share of a record-setting $8.9 billion penalty against the French bank BNP Paribas for doing business with Iran, Syria and other rogue regimes in violation of U.S. sanctions.

Nor can it expect in the future to pocket hundreds of millions in penalties from Crédit Suisse, Citigroup and other companies.

Despite their fleeting nature, the payments have set off the beginning of a predictable feeding frenzy. The Alliance for Quality Education called them “a great opportunity to actually fund our schools” — without explaining how such funding would be sustained when the windfall runs out.

Among those seconding that idea were state Senate Republicans, who claim to be a bulwark against budgetary recklessness. Just as reckless, they proposed allocating some of the money to roll back taxes and fees.

A far saner plan was laid out in a July 17 Daily News op-ed coauthored by liberal former Assemblyman Richard Brodsky and fiscally conservative watchdog E.J. McMahon of the Empire Center for Public Policy.

The ideological odd couple proposed sinking the entire sum into transportation infrastructure, with half earmarked for chronically underfunded New York City-area mass transit and half for upstate roads and bridges.

In the same sensible vein was Monday’s statement from the state Budget Division, which said the Cuomo administration “is developing options for using the surplus prudently, which may include funding one-time capital expenses, bolstering reserves and reducing debt.”

Yet the next day, the governor himself sent a very different message with his loose talk about schools and tax cuts.

“Can we finally, without regard to left or right, act in a fiscally responsible way?” McMahon and Brodsky wondered.

Well, governor, can we?