Originally Posted by
dougie_504
When empty/light on:
Pro = old petrol doesn't stay in your tank/go stale
Con = more likely to pump in any sediment/debris that settles in the bottom of the tank when it gets emptier
When 1/4 or greater = see previous and just reverse them.
Best thing to do IMO is clean out your tank or just fill up when you hit approx 1/4 or close enough to it, but the difference you'd see in petrol deterioration and your engine sucking up debris/sediment is negligible IMO and probably more just theory than fact.