I have been reading more reviews about driving in a high gear at low speeds to achieve fuel economy. I have tried this since and can happily plod along at 30mph in 5th gear (manual) on a reasonably level road. The rpm is around 1000, how is possible that I can take my foot of the accelerator and the engine will continue to turn over and run at a near constant 30mph?

The mpg has been anywhere from 60+, also will this be potentially causing any engine damage? Much obliged to hear you thoughts.