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Recommended fuel

5K views 3 replies 3 participants last post by  Dmac47 
#1 ·
Ex-t and above civics have 10.6-1 compression ratio. 2017-18 si has 10.3-1 ratio. Why does Honda recommend 87 octane for 10.6-1 and 91 for 10.3-1?
 
#2 ·
It's not in the compression ratio as much as the ECU mapping. The sport hatch recommends 91 and it has the same ratio as the other HB's. If you flash your ECU you tune (map) to your desired octane, the higher the octane the more HP you can get without detonation.
 
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