THE DISTRICT'S council members had barely driven home from a solid vote to impose a 6 percent gasoline tax when some of them began to get cold feet. Service station owners, predicting the end of their world if the tax is allowed to take effect, promptly stirred rumblings among the city legislators about some sort of compromise; and now a hearing is set for July 16 on proposals for a lower tax. Though no one relishes the idea of a stiff tax, the council should stick to its earlier decision.

The cries of "crisis" have been led by Vic Rasheed, executive director of the Greater Washington-Maryland Service Station Association. Mr. Rasheed claims that the 6 percent gas tax, which will add an average of 7 or 8 cents more to the price of a gallon, could cut sales in the District by 40 percent -- forcing some stations to close and others to lay off employees. City tax officials estimate a 16 percent drop in sales as a result of conservation and some motorists' buying in Maryland, where there has been no tax increase.

There is no question that some District service stations near the Maryland line will suffer -- temporarily. Even without any new tax, this situation occurs already, right within the city limits: the station owner who charges higher prices than his competitor down the street stands to see a lot of traffic whizzing on by the better buy. Still, as owners well know, there's a limit to how far a motorist will drive at today's per-mile rates to attempt a savings.

Besides, it is only a matter of time before the gas tax seesaw will swing again, putting some other jurisdiction ahead of the District. For example, Northern Virginia is on top for the moment, having just added two new gas levies this month -- a statewide 2-cents-a-gallon tax plus a 2 percent tax in Alexandria, Arlington, Fairfax, Falls Church and Fairfax City. As For Maryland, there was talk this year of a gasoline tax, but because of a state revenue surplus, the legislators didn't have to go that route to make ends meet.

Ends aren't meeting at all in the District -- and that is precisely why Mayor Barry and the council tackled the grim job of raising local gas taxes right away, in a determined effort to offset a budget deficit in the current fiscal year that ends Sept. 30. If station owners or low-income residents can demonstrate serious injury from the proposed tax increase, the mayor and the council can come up with ways to provide some relief. And with a little effort, some motorists may find they can cut their driving down just enough to keep their gasoline bills the same. Otherwise, how else do people want their taxes raised? If the council members waver on this one, they'll just have to take it out on taxpayers some other way. The council members have done what they should in shot order -- and given the state of the city's finances, there is neither time nor cause for any after-the-fact political tinkering.