MAYBE CITY HALL can run a good lottery, but when it comes to figuring out gas-tax rates, the Barry administration certainly hasn't been all that hot with its numbers. As a result, motorists as well as service station owners in the District have been given quite a runaround since August, when Mayor Barry first socked them with a 6 percent sales tax at the pumps. At that time, official calculations from the great Municipal Abacus indicated two things to an unhappy public: the city government desperately needed more money, and the new tax would produce a good $13 million more for the coffers over three years.

Boo, cried the motorists and station owners, and -- lo and behold -- within a scant three weeks word had it that the mayor was thinking about repealing the tax. All this while, any motorist within coasting distance of the District line was rolling into the suburbs to save as much as $2.25 a tankful. While the mayor mulled and mulled, so did Maryland Gov. Harry Hughes -- who, too, had once talked about pushing for a gas-tax increase in his state but who also had second thoughts.

So now, with a revised set of numbers, comes Mayor Barry again, moving quickly to wipe out the 6 percent gasoline sales tax entirely. It seems the city isn't to so severely strapped that it needs this tax at all; instead, the mayor and the council have added a penny to the current 10-cents-a-gallon excise tax on gasoline. That won't make up all the revenue losses from dropping the sales tax; but never mind, says the mayor, it can be replaced with money generated by a new law allowing the government to receive funds from private bank accounts that have been dormant for seven years.

If you can figure out what difference all of this makes in the general financial condition of the city -- not to mention its constant pleas for higher federal payments -- you can keep the change. But why such a stark reversal, from a hefty levy on gas sales to total repeal and a tinkering with another tax? If the city's numbers were so off-base before, how long will it be before officials discover that revenue losses are much bigger than they ever dreamed, necessitating an ugly reprise of the 6 percent deal?

Meanwhile, back at the governor's office in Annapolis, there's no telling what Gov. Hughes has punched up on his gas-tax calculator. It's not that they have to do everything in tandem, but maybe Mr. Barry and Mr. Hughes should discuss the outlook for gasoline taxes and prices in their respective jurisdictions, and then act somewhat according to minimize the impacts both on consumers and service station owners while maximizing reasonable revenues. Any odd or even day of the month would do.