My 2017 Hyundai 2.4L GDI engine runs sluggish with 87 octane in high heat & humidity ... Conversely using high octane (92 or 93) makes a significant difference in engine pep during high heat & humidity . I'm not sure why higher octane makes such a difference in Summer months with improved engine performance - I'll switch back to 87 octane in the Fall when temps & humidity drop again . Your thoughts & experiences ?