Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum - View Single Post - Regular Unleaded Gas (stock) vs Premium Unleaded Gas (tuned)
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Old 03-27-2012, 07:51 PM   #47
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Tom is correct. If the computer senses any knock, it will start to retard timing. Yes our cars will knock slightly on 87 octane, its not uncommon to see the computer retard timing by 2-4 degrees. The use of midgrade or premium fuel will make sure the timing stays at full advance. Now granted with premium fuel there is room to add a few degrees of timing at WOT. For a untuned Focus, 89 octane in most cases is good enough.
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