I have been on several longer trips with my 1,8 and never had this issue.Well i finally let the engine settle and go cold and checked the dip stick... Pleased to see that there is still plenty of oil in there. Bearing in mind i went on an 200 mile journey the day the warning message came up. So my theory is that if you drive for long periods of time, i assume all the oil moves around and sticks to the side and falsly sends out a warning message because it thinks its low, when its not! :-?