The pilot planned two flights from Tyabb to Melbourne Airport and return. Prior to DEPARTURE he refuelled the left tank of the aircraft to full and estimated that fuel onboard was then 88 litres. He nominated a fuel endurance of 150 minutes. The planned total flight time was 92 minutes. No problems were encountered on the first return flight which took a total flight time of 59 minutes. On the second flight to Melbourne the aircraft was held for about 15 minutes, due to other traffic. When taxying for DEPARTURE from Melbourne the pilot noticed the fuel gauges were reading empty, but because these do not read accurately in the ground attitude he did not accept the indications as reliable. After take off the aircraft was climbed to again cruise at 3000 feet. When in the vicinity of Williamstown the pilot noticed both fuel gauges were indicating near empty. The aircraft was rolled and the pilot noted the gauges moved, indicating to him that there was some fuel in each tank. The pilot decided that there was no need to declare an emergency. A decision was made to refuel at Moorabbin but a descent clearance was not available. After vacating controlled airspace, just south of Moorabbin, he advised that the aircraft would divert to Moorabbin. Just as he did so the engine failed and a forced landing was carried out onto a racetrack. The aircraft ran through a fence during the landing roll. Draining both fuel tanks produced about half a litre of fuel. The pilot stated that the mixture had been leaned for all the flights. The total flight time up until the time of engine failure was approximately 125 minutes. In doing his fuel consumption calculations the pilot did not allow for fuel used on taxy/takeoff and the higher consumption rate on climb. Instead he worked on a lean mixture consumption rate for cruise. Calculations using the manufacturers consumption figures found that all usable fuel would have been consumed at the time of the engine failure. There was no reason why the pilot could not have started the flights with full tanks or have refuelled in between them.