there r no end to myths, legends, facts, etc into saving petrol.
if i tell u grounding ur electrical circuitry enhanced with a voltage stabilizer saves petrol, wld u believe it?
even changing a simple air intake filter to something like K&N or hurricane filters (relatively inexpensive compared to changing the whole intake) will give u HP gain and saves petrol.
........ and i dun even carry a spare tyre in my boot.