10:80 to 1 compression ratio on a V6 2011 Sienna. Best octane gas for this?

I have been told 10:1compression ratio or less can use 87 octane without any problem.....my engine is 10.80-1 compression ratio--V6 and is a 2011 Toyota Sienna. The manual says I can use all three 87, 91 or higher...how can this be? What would you expect the best octane to be for this engine. Thanks....can't get a straight answer from toyota. Really need your help and input!