This question gets asked over and over again and I am still baffled that people buy a Bimmer and than want to skimp on the gas they put in it to save $2.00 per tank. BMW's are made to run premium fuel, it keeps them at their peak and clean, due to additatives that regular fuel does not have. Yes your car will run on regular and or mide grade because the system will adjut to perform on the lower octane. However it will not be running at peak performance and over time will damage the engine!