Oil has a finite life once in an engine: mileage is only one side of the equation. Really a case of weighing up the type of running it's had, how long it's been idle, storage conditions, direction of the wind, exchange rate of the yen to the Columbian Peso, etc, etc.... For what an oil change costs, if you're in any doubts at all, change it. By asking the question, you have doubts!