* The United States government could save $15 billion over the next three years by ''overhauling'' the civil service retirement system.
* And $3.5 billion could be saved by altering the way a household's food stamp total is figured, reflecting demographic changes of the last 20 years.
* Eliminating the National Oceanic and Atmospheric Administration's weather radio service might save $11 million a year.
These are a few of the cost-saving suggestions contained in a just-released preliminary report of the President's Private-Sector Survey on Cost Control.
In June, the PPSSCC will issue a full report listing possible savings of at least $60 billion a year, says businessman J. Peter Grace, head of the group. But judging by the preliminary list, issued Tuesday, many of the recommendations are more than mere management changes, and are likely to be politically controversial.
''We did not try to evaluate the political sensitivity (of these suggestions) ,'' says Felix Larkin, chairman of the executive committee of W. R. Grace & Co. and a committe member. ''It's up to somebody else to do that.''
President Reagan, like many of his predecessors, came to Washington promising to cut waste, mismanagement, fraud, and abuse out of the federal government. Establishing the PPSSCC was one of his first actions as president.
The group is a task force of 1,300 private-sector volunteers deployed throughout the government in search of wasteful management, outmoded procedures, and all-around sloth, according to its members.
But congressional critics have viewed the group with suspicion, saying that it was violating the spirit of federal disclosure laws with secretive ways, and that it was considering cuts that went beyond questions of efficiency into matters of policy.
Critics last month, for instance, charged that the PPSSCC was considering a recommendation that the Veterans Administration be abolished. Mr. Grace retorts that such an idea was simply written on a ''scrap of paper,'' and was never considered seriously.
''This whole (controversy) is ridiculous,'' says Grace. ''I'm just down here to help.''
On Tuesday, the panel released preliminary recommendations from six of its 36 individual committees. The cost-saving suggestions would save $54 billion stretched out over the next three years, according to PPSSCC figures. The survey's executive committee must still give the preliminary reports a final seal of approval.
The biggest chunk of savings, $15 billion over three years, would come from ''overhauling'' the civil service retirement system.
''This is a sensitive area, of course,'' says Mr. Larkin. ''We are not trying to injure federal employees.''
Federal employees may not see it that way, however. Specific changes recommended in their pension system include raising the minimum retirement age to 62 (currently it is 55 for employees with 30 years' service), changing the way their basic annuity is figured, and basing their annual cost-of-living adjustment on whichever is lower, the consumer price index or the annual overall General Services pay increase.
The next largest saving suggestion involves another politically sensitive program - food stamps. Currently, many food stamp benefits are figured on the assumption that the average household contains 4.6 people. That may have been true when the program began, but the latest figures put the average household at 2.6 people, says Larkin.
''Changing the food stamp allotment would bring the program more in line'' with reality, he says, though the change would mean a cut in benefits for those now on the rolls.
Other suggestions of the PPSSCC include:
* Count children's free school lunches as household income in determining food stamp benefits, a move the PPSSCC estimates would save $1.7 billion over three years.
* Cut an ''unnecessary'' $1.2 billion from strategic petroleum reserve operations.
* Scale back plans for the Patent Office to hire more examiners and computerize its operations. Estimated savings: at least $86 million by 1990.
* Raise prices on National Oceanic and Atmospheric Administration maps and charts by 25 percent.
* Close six Environmental Protection Agency regional laboratories.