pinging

[sg11]

So for a while now I've noticed that my engine seems to what I believe to be pinging and since it has gotten hotter out it seems to have become more pronounced as pinging does in warmer weather. I've been reading a lot on here and in general about the subject. From the info I have gathered it seems some light pinging is normal and that it is common with the Yaris and even though the manual suggests an 87 or HIGHER octane fuel the general consensus seems to be that putting in anything more than 87 is a waste of money. From what I have read the Yaris with its 10.5:1 compression ratio engine is considered to be high compression. My question is if a car such as the newer Honda Civic Si which has a ever so slightly higher compression ratio of 11.0:1 requires premium fuel then why does the Yaris only require 87?