Spent the day on Salisbury Plain (in the UK) today covering almost 100 miles from home and back. Thought engine was noisier than usual when I set out. It got progressively noisier to the point where for the last 20 miles it sounded like a rough old tractor. Should have stopped and checked earlier but just wanted to get home. Anyway, checked oil (the proper way) when at home and it was not registering on the dipstick at all. Thought I would 'top it up' and put almost 2l in before reaching the full level. So she was running on empty I reckon for the last few miles. Anyway, miraculously, she sounds pretty good now and I can't see any obvious damage in terms of performance. Do you think I've got away with it, or am I likely to have damaged something?