 Today's modern vehicle, whether it's a car, SUV, or light truck, is designed with a specific fuel in mind. Read your owner's manual. What octane rating does the vehicle manufacturer call for? That's what you should use. But there are exceptions to the rule. Many high-end or luxury vehicles call for premium or higher octane fuel. And the reason for this is not just due to the octane rating. There are better fuel system cleaners in premium fuels.