Octane is up to you, generally the higher the octane used the greater the performance. I don't have a programmer for my G6, but I have an SCT for the Durango and at the most I'll run 91 octane. US equivalent we pay $1.412/USgal more to go from 87 octane to 94. It's only a few cents less to drop down to the 91 octane from 94. Only two stations in my city of over a quarter million people sell 94 octane.
Octane here is 87, 89 ,91, 94.
'11 Ram SXT 4x4 quad cab - 5.7L V8; 128,200kms
'09 Malibu 2Lt 3.6L - 140,000kms purchased 1 March 2019
'06 Pontiac G6 GT - 3.5L V6; 162,000kms (rear ended 15 Feb 2019, and given totalled title by insurance)