I find all these differences interesting as I have done 1700 miles and when I checked my oil it was on the minimum. Being new to the marque I was quite surprised it had used so much oil. I have driven gently, I've driven it quickly, on B roads, A roads and motorways, so a bit of everything. Having had several focus I have never had to top up between services even when I had a ST with the 5 cylinder turbo charged engine.
But I suppose every engine is different, and although I don't think I have treated this car any differently from the others, its not an exact science. I'll just have to make sure I keep a closer eye on oil levels in future.