A C206 PLT; UPON RUNNING 1 FUEL TANK EMPTY; CONTINUED THE FLT USING FUEL FROM THE ONE AND ONLY REMAINING TANK UNTIL THE ENG 'SPUTTERED;' LEAVING SPECULATION THAT THIS TANK WAS ALSO EMPTY. AN OFF ARPT LNDG WAS THE RESULT.

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ON APR/TUE/02; APPROX XA20; I DEPARTED MTN DIRECT ESN FOR A PLEASURE FLT TO CHK A GPS MOVING MAP WE RECENTLY HAD SVCED THE PRIOR DAY; ALONG WITH A FLT INSTRUCTOR AND 1 OTHER PAX. THE WINDS WERE 340 DEGS; WINDS 12 KTS GUSTING TO 15 KTS; VISIBILITY 10 MI. SKY WAS CLR. AFTER LNDG AT ESN; WE TAXIED TO RWY 33 AND DEPARTED BACK TO MTN. BEFORE TKOF; WE VISUALLY NOTED WE HAD 13 GALLONS IN THE L WING AND 15 GALLONS IN THE R WING ACCORDING TO THE FUEL GAUGES. I SWITCHED TO THE R FUEL TANK FOR THE RETURN FLT TO MTN; WHICH WAS 35 NM; APPROX 22 MINS FROM OUR FLT HOME IN APCH ROCK HALL; MD; APPROX 12 NM SE FROM MTN. AFTER OBTAINING THE ATIS; I NOTICED A SPUTTER FROM THE ENG. I QUICKLY NOTED THE R FUEL WAS READING EMPTY; SO I SWITCHED TO THE L FUEL; WHICH STOPPED THE SPUTTERING. AT THAT TIME I DECIDED TO NOT CONTINUE TO CROSS THE CHESAPEAKE BAY TOWARDS MTN. I DIVERTED TO RIDGLEY ARPT TO REFUEL; WHICH WAS APPROX 10 NM E OF WHERE I WAS. WITHIN 1-2 MINS; I EXPERIENCED THE SPUTTER SOUND AND I DECIDED TO NOT CONTINUE WITH THE FLT. I WAS NOT SURE WHAT THIS SOUND WAS; SO I BRIEFED MY PAX THAT WE NEEDED TO DO A PRECAUTIONARY LNDG TO FIND OUT WHAT THE NOISE WAS. I LOCATED A FIELD AND SAFELY LANDED. AFTER VISUALLY CHKING THE WINGS FOR FUEL I NOTED THE L WING WAS VERY LOW TO EMPTY AND THE R WING HAD APPROX 2 1/2 INCHES OF FUEL. I CALLED FOR FUEL; AFTER OBTAINING 30 ADDITIONAL GALLONS OF FUEL; I DECIDED TO DO MY ROUTINE RUN-UP AND PROCEEDED WITH A SOFT FIELD AND SHORT FIELD TKOF. WE CONTINUED TO MTN AND RETURNED SAFELY. NO OTHER PROBS WERE NOTED AFTER MAINT SHOP EXAMINED THE ACFT. I BELIEVE THAT DUE TO THE STRONG HEADWINDS OUR FUEL BURN WAS MUCH GREATER AND THE FUEL GAUGES MAY BE SLIGHTLY OFF.