Only once, atleast 2 oil changes are necessary to keep power of vehicle at peak, before break in period is finished. Best to give car oil change right after buying before using in a race unless, you are trying to keep cars PP level low for a PP regulated event like a Seasonal TT or ASpec event.
In my experience, I usually get first power drop at 95 miles second at 185. Once a Vehicle hits 10,000 miles all power losses are permanent regardless of engine rebuild or oil changes.
At 3890 miles you must rebuild engine to keep power at peak, as an oil change will only bring back some HorsePower.