Can you put regular gas in a Lexus gx470?

no, you can not. Only gas that you should use is unleaded I think he meant 87 octane. You can absolutly use 87 octane in the tank but you may not get the same performance or gas mileage. It will not harm the engine or fuel system at all but you may get what is refered to as a "spark knock." This again will not damage the engine. I suggest you experment with the different types of octane. In mine, I found it was overall worth while to go with premium. In my geographic region, my mileage and performance do best with this type, you may find the lower octane savings is not trully that because of a more effiecent useage of premium fuel.