Load of crap. The fuel pump ALWAYS sucks from the bottom of the tank (as that is where it sits), so if there is sediment there it _will_ suck it up, even with a full tank. This is why you have fuel filters, to stop that crap getting into the engine. Generally you're recommended to not run below a certain amount because of the possibility of starving the fuel pump (even with baffled tanks, this can happen), as well as the high-pressure EFI in-tank pump relies on the fuel to lubricate it (so if it runs dry too much the pump gets rooted). If the pump starves long enough you'll get a significant reduction in fuel-rail pressure, and that can make you run lean, which is not good for the engine (nor the catalytic converter either) the etc was what i meant with additional damage being done. only stating whats in the book plus what mechanics have told me.