A B737 FLT CREW OPERATING AS A PASSENGER FLIGHT WITH THE LANDING GEAR INOP IN THE EXTENDED POSITION FOUND THE FUEL FLOW TO EXCEED THE BOOK VALUES; AND DECLARED A FUEL EMERGENCY TO EXPEDITE THEIR ARRIVAL HANDLING AT DESTINATION.

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I WAS THE CAPT OF FLT X TO ZZZ. FLT WAS BOOKED FULL; WITH MEL LNDG GEAR LOCKED IN THE DOWN POS. THIS WAS AN UNSCHEDULED ACFT CHANGE. UPON ARRIVING AT THE GATE THERE WAS CONFUSION AS TO WHETHER WE WOULD FERRY THE ACFT OR REVENUE THE ACFT TO ZZZ FOR FURTHER MAINT. AFTER CONTACTING DISPATCH; WHO CONTACTED THE DUTY MGR; THE DECISION WAS MADE TO CARRY PAX AND FLY WITH THE GEAR DOWN PER THE MEL. THE FIRST DISPATCH RELEASE DID NOT HAVE THE MEL LISTED. DISPATCH WAS NOTIFIED AND A NEW RELEASE WAS ISSUED. ALTHOUGH FUEL WAS ADDED FOR THE MEL; THE FLT WAS FILED AT 340 KTS TAS. DISPATCH NOTIFIED AGAIN. DURING THIS CONVERSATION WITH THE DISPATCHERS I ASKED IF THEY HAD A 'GEAR DOWN' FLT PROFILE. NO PROFILE WAS FOUND; ALTHOUGH WE DID DISCUSS THE 'GEAR DOWN; LONG RANGE CRUISE' PROFILE CHARTS IN THE PERFORMANCE SECTION OF THE OPS MANUAL. THE FUEL FLOWS LISTED IN THIS SECTION CLOSELY MATCHED THE FUEL CONSUMPTION THAT DISPATCH HAD PLANNED. I VOICED MY CONCERN THAT ANY ATC DIRECTED DEVS FROM THE FLT PROFILE DUE TO THE SLOW CRUISE AIRSPD OF THE FLT WOULD VOID THE FUEL PLAN. DISPATCH STATED THEY WOULD CONTACT ATC AND NOTIFY THEM OF THE SITUATION. I THEN COMPARED THE FUEL FLOW FIGURES FROM THE FILED CRUISE ALT AND THE LOWEST LISTED ALT (17000 FT) AND NOTED THAT THERE WAS ONLY A SLIGHT INCREASE IN FUEL FLOW AT THE LOWER ALT; LEAVING ME TO BELIEVE THAT IF THE FLT WAS FORCED TO STAY AT A LOWER ALT (17000 FT) THE ENTIRE WAY TO ZZZ; THERE WOULD ONLY BE A CORRESPONDINGLY SLIGHT INCREASE IN TOTAL FUEL CONSUMPTION. PRIOR TO BOARDING I WENT TO THE GATE AREA AND USED THE PA SYS TO EXPLAIN THE SITUATION TO THE PAX AND THAT THE GEAR WOULD BE LOCKED DOWN THE ENTIRE FLT; RESULTING IN A NOISIER AND BUMPIER FLT THAN NORMAL. I THEN DISCUSSED THE FLT WITH THE FO REGARDING FUEL CONSUMPTION; PAX COMFORT AND PERFORMANCE ISSUES INCLUDING LOSS OF ENG WITH GEAR DOWN. THE FO NOTIFIED CLRNC DELIVERY OF OUR AIRSPD AND CLRNC DELIVERY SAID THEY WOULD PASS THE INFO ALONG. THE OPS AGENT HAD TO ADJUST THE PAX LOAD AND USE CHILD WTS TO BRING THE ACFT BELOW ATOG DUE TO THE INCREASED FUEL LOAD. THE GND TIME WAS HECTIC. TALKING WITH MAINT AND DISPATCH; DEALING WITH A NEEDY 'A' FLT ATTENDANT AND A SKITTISH OPS AGENT WAS TIME CONSUMING. ATC HANDLED THE TAXI; TKOF AND CLB PORTIONS OF THE FLT VERY EXPEDITIOUSLY. CTR CHANGED THE ARR TO SHORTEN THE RTE. THE FUEL BURN AT TOP OF CLB AND OVER AND ENRTE MATCHED THE FLT PLAN EXACTLY. PRIOR TO LEAVING THE AREA BEHIND; I WANTED TO BE SURE THAT THE FUEL CONSUMPTION WAS AS PLANNED. APPROX 200 NM FROM ZZZ ATC GAVE THE FLT A DSCNT CLRNC. THE FO REQUESTED THAT WE STAY AT ALT; BUT ATC MADE ALL THE REMAINING DSCNT CLRNCS MANDATORY. THE FUEL OVER THE NEXT VOR WAS 100 LBS LESS THAN WHAT THE FLT PLAN INDICATED SHOULD BE REMAINING. THEN A MANDATORY DSCNT TO 17000 FT WAS GIVEN. THE FUEL FLOW AT 17000 FT WAS MUCH HIGHER THAN AT ALT AND FAR EXCEEDED THE FUEL FLOWS LISTED IN THE OPS MANUAL PERFORMANCE SECTION. THE 'A' FLT ATTENDANT CALLED THE COCKPIT TWICE DURING DSCNT TO REQUEST GATE INFO. THE WINDS AT ZZZ HAD SHIFTED FROM EASTERLY TO WESTERLY AND WERE GUSTING TO 17 KTS; NECESSITATING A LNDG TO THE W. CONTACTED DISPATCH TO LET THEM KNOW ATC WAS FORCING THE FLT LOWER; WHICH WAS CONSUMING MORE FUEL. THEN WE GOT A CLRNC TO CROSS 15 NM W OF XXX INTXN AT 10000 FT. THE FO REQUESTED TO STAY AT ALT BUT THE REQUEST WAS DENIED. THE HIGHER THAN PLANNED FUEL CONSUMPTION AT THE LOWER ALTS AND FUEL CONSUMPTION REQUIRED AT 10000 FT WOULD HAVE MEANT AN UNACCEPTABLE ARR FUEL AT ZZZ. A FUEL EMER WAS DECLARED AND THE ACFT WAS LEVELED AT 16000 FT AND PROCEEDED DIRECT TO ZZZ. WITH ATIS WINDS NOW LIGHT AND VARIABLE; MADE AN UNEVENTFUL LNDG AT ZZZ. FUEL AT THE GATE WAS 4200 LBS. I SHOULD HAVE ADDED MORE FUEL EVEN THOUGH IT WOULD HAVE MEANT PULLING MORE PAX. THE FUEL FIGURES ON THE FLT PLAN APPEARED TO BE SOUND BUT HAVING NEVER FLOWN WITH THE GEAR DOWN; I DID NOT KNOW WHAT TO EXPECT AND SHOULD HAVE PLANNED FOR THE WORST CASE. GET MORE PEOPLE INVOLVED IN THIS ABNORMAL SITUATION. I WANTED TO TALK WITH SOMEONE THAT HAD FLOWN GEAR DOWN OR HAD KNOWLEDGE OF WHAT TO EXPECT. HAVE A BRIEFING FOR THIS SPECIAL FLT OP. DEVELOP A GEAR DOWN FLT PROFILE DETAILING CLB AND DSCNT SPDS AND RATES. PLAN THIS FLT FOR WORST CASE SCENARIO. AT AN AIRSPD BELOW 220 KTS; I WAS CONCERNED ABOUT VECTORS OFF COURSE AND THE INEVITABLE LOWER ALT. SHOULD WE HAVE KNOWN THE FLT WOULD BE GIVEN LOWER ALTS SO FAR FROM THE FIELD? LIST THE OPC; MEL GEAR DOWN CRUISE PAGE AS A REF TOOL; PERHAPS AS AN MEL STEP. CHK THE FUEL FLOW SPECS. THEY MATCHED THE PERFORMANCE OF THE ACFT AT FL230 EXACTLY; BUT AT THE LOWER ALTS THE REQUIRED FUEL FLOWS WERE HIGHER THAN PUBLISHED. IN THE QRH LNDG GEAR SECTION LIST THE OPC; MEL GEAR DOWN CRUISE PAGE AS A REF. GEAR LEVER WILL NOT MOVE UP AFTER TKOF IS ONE POSSIBLE LOCATION.