MY FD ONLY TAKES ME 450km FULL TANK AND ITS BRAND NEW

[ido09s]

1) Accelerate slowly - careful on the gas...the more slowly you step on the pedal reduces the chance of you injecting big globs of fuel into your engine which doesn't get burnt.
4) wind up your windows if you dont have window visors as it affects fuel consumption...about 0.5L/100km at least..
5) where possible do not use heater/AC, saps at least 1L/100km

Your kidding arent you.... who told you all this stuff

If your engine is 'injecting big globs of fuel into your engine which doesn't get burnt' then you need to get it checked by Honda as your engine should be burning all the fuel regardless of throttle position.
Winding down your windows does nothing unless you plan on travelling at extreme speeds. I dont believe everything i hear but i dare say thet Myth Busters would be pretty correct with their findings.
The heater will not use any more fuel even if you have it turned to full hot. All the heater does is circulate water through the heater core and the air from the fan is directed through this core to heat the air.
A/C on the other hand is a different matter as it needs the A/C compressor to cool the air entering the interior

As for fuel economy....
I have a manual FD1 that i religiously run on Caltex E10 and i have no problems getting between 550 and 600klms per 42 litres around town including peak hour traffic

I dont know just how much extra power people are expecting to gain by running 98 octane but lets remember here guys its a naturally aspirated 1.8 litre engine. The gains to be had by using 98 octane may be at most 5kw's and you will never feel the difference with such a low power gain.