For people from out of WA we have a strange petrol pricing system in WA. Prices can only be changed at 6.00 am each day.
Currently it is a weekly cycle. For most service stations the highest price is from 6.00 am on a Tuesday. It will then drop several cents daily until to reaches a low on Monday jumping up 15 to 20 cents at 6.00 am Tuesday to start another weekly cycle.