Hi there!
This question comes up more times than the morning Sun. As Lenor has said, It used to be a requirment that only Premium,(91 octane) was approved for purposes of warranty coverage. Since around 2013 the Owners Manual indicated that the use of regular (87 octane) was approved, and you could choose either products without any difficulty. When we bought our 2013 ES 350 and our 2013 RX 350, I decided to try using only 91 octane. That has been about 2 1/2 years. No problems, no ping.
Now with Petrol so cheap, I've changed to 87 octane with no problems and still with-in the warranty demands. I don't notice any difference with the two, but I don't do much highway driving so it is difficult to judge any difference in mpg.