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Is E15 bad for stock high performance cars?

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Hi, this is coming from someone with very little tuning knowledge.

But as far as I know, ethanol fuel has a richer stoichiometric AFR than regular gasoline. On E15 it would be 13.8:1

So on stock cars without a tune, the ECM would be targeting an AFR that is on the lean side for E15 gas since all of its fuel maps are based on regular gasoline.

Would that cause problems like detonation, especially for a high performance car, at high rpm/load? Can the factory ECU knock control compensate for this? Or is it already handled by closed loop fuel control?

I'm asking this because my country is going to replace all unleaded fuel with E15.

I am following this post to learn, we have an E10 supply readily available here.