On the MC28, if you remove the oil injector system and dont deal with the oil level sensor, you could end up with the oil warning light being on all the time.

If you simple blocked the oil tank, leaving some oil in there and the sensor still hooked up, you could see the warning light every once in a while depending on conditions (bike leaned over and the little bit of oil moving in the tank, etc..).

If your running pre-mix, I wouldn't worry about the oil light.