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depends on what your goal is. A 0% utilization rate can actually knock a few points off your scores. If scores are what you're after, i.e. you're going for something big in the next month, then leave a very small balance on the account. If your goal is to show responsible use of credit to Capital One then what the statement shows for a balance doesn't matter, as long as you pay it all off on time.
If you've had the card for five months I would recommend looking at an unsecured Cap One card, then use it as much as possible and pay it down when necessary. That should net you a nice CLI in a few months.
Current wisdom here is all cards at 0 except for one card between 1-9% for optimum util scoring.