ACR MLG CAPT DISPUTED AN ATC CLRNC THEN FAILED TO MAKE AN ALT XING RESTRICTION DURING A STAR INTO LGA.

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INBOUND TO LGA; ON THE MILTON STAR; THE NY APCH CTLR ASSIGNED US A SPD REDUCTION OF 190 KTS. I REPLIED THAT I DESIRED TO MAINTAIN 210 KTS; AS WE WERE STILL 31 NM FROM THE ARPT; AND I WANTED TO KEEP FROM CONFIGURING THE ACFT UNTIL A MIN OF 20 MI FROM THE ARPT SO S TO SAVE FUEL (CLEAN ACT CONCEPT). WE WERE FORCED TO REDUCE TO 190 KTS. AFTER THE CTLR FURTHER EXPLAINED SHE WOULD HAVE TO 'PULL US OUT OF THE ARR SEQUENCE' IF WE DID NOT COMPLY. THE AIM SAYS THAT SPD ADJUSTMENTS BELOW 210 KTS MORE THAN 20 NM FROM THE ARPT ARE TO BE ASSIGNED ONLY WITH 'PLT CONCURRENCE.' FURTHER; SPD ADJUSTMENTS BELOW 170 KTS ARE ALSO ONLY TO BE ASSIGNED WITH 'PLT CONCURRENCE'; AND ONCE AN APCH CLRNC IS ISSUED NO FURTHER SPECIFIC SPD ASSIGNMENTS WILL BE ISSUED BY ATC. AFTER WE WERE 'CLRED FOR THE ILS TO RWY 04 AT LGA'; THE CTLR ASKED US TO CROSS THE GREENE INTXN (11.1 DME ON THE ILS) AS CLOSE TO 2700 FT MSL AS POSSIBLE. I WAS UNCOMFORTABLE 'DUCKING UNDER' THE GS; 3 MI IN TRAIL OF A JET AHEAD OF US; AND I INITIALLY THOUGHT THAT SHE MEANT 2700 FT OR ABOVE; TILL XING THE GREENE INTXN (11.1 DME). SHE MEANT AS CLOSE TO 2700 FT AS POSSIBLE. THIS WAS DIFFICULT TO DO AT OUR ASSIGNED SPD OF 170 KTS. AT GREENE; WE WERE TOLD TO REDUCE FURTHER TO OUR MIN APCH SPD (WE CROSSED GREENE AT 3000 FT; 11.1 DME). RECOMMENDATION: ATL SHOULD NOT REDUCE JET ACFT BELOW THE MIN 'CLEAN' MANEUVERING SPD UNTIL ABSOLUTELY NECESSARY (SUGGEST NO SOONER THAN 15 MI FROM A COURSE DIRECTLY ENRTE TO THE RWY ON AN APCH). THIS WILL SAVE A TREMENDOUS AMOUNT OF FUEL; ALSO; SUGGEST THAT ATC REREAD THE AIRMAN'S INFO MANUAL; REF SPD ASSIGNMENTS FOR ATC ACFT IN THE TERMINAL AREA. I WOULD MUCH RATHER HOLD THAN 'DIRTY-UP' EARLY; UNNECESSARILY. PS; ALSO; PLEASE KEEP JET ACFT AS HIGH AS FEASIBLE AND USE A 3 DEG GS DSCNT.