I'm not saying it's now void but if something oil related happens to the engine and Hyundai sees you didn't change the oil on time, they could try to void your warranty. The chances are slim that they could but it is a possibility.

If you want to extend your maintenance schedule to longer time and/or miles than the manufacturer suggests, I'd wait until after the warranty has expired. Doing it during the warranty could give the manufacturer grounds to void the warranty.

Right, the oil has already been changed. Thanks.