What compression ratio determines the octane rating needed for a vehicle? Let me site an example with two similar engines:
Mitsubishi Eclipse
V6 3.0L SOHC
CR: 9.0:1 (GT) Req Fuel: Premium Unleaded
CR: 10.0:1 (GTS) Req Fuel: Premium Unleaded
Honda Accord
V6 3.0L SOHC
CR: 10.0:1 Req Fuel: Regular Unleaded
Compression Ratio for the Honda Accord is 10.0:1 and only requires Regular Unleaded.
But why does the Mitsubishi Eclipse having both 9.0:1 and 10.0:1 compression ratios require premium unleaded?