I with mistermac.
I follow the manual to all my cars. If it required 91 or higher I will only put in 91 or higher. Oil company always mislead customers with they say their "premium" gas is better. Using lower octane to car that design for it won't cost more pollution and knock. I saw a test that using 91 octane to a car that not required 91 cost more pollution. If yes government should ban 87 and 89. Now day all top tier gas company will have same amount of cleaning agents to all octane gas. As for recommended and required, my manual do say the same like nismopdb, but it only for optimal performance they recommended 91 or higher, not required. And it say maximum performance on unleaded fuel and again not premium unleaded fuel. It didn't mention anything that say using octane rating lower than 91 will cost damage (my sti manual had mention). Only when the engine is knocking and need to try upgrade to higher octane. I used to drive a Camry v6 that recommend premium But I fill 87 for 10+ years never have a problem. So many people still mistaking higher octane number mean better fuel.
I follow the manual to all my cars. If it required 91 or higher I will only put in 91 or higher. Oil company always mislead customers with they say their "premium" gas is better. Using lower octane to car that design for it won't cost more pollution and knock. I saw a test that using 91 octane to a car that not required 91 cost more pollution. If yes government should ban 87 and 89. Now day all top tier gas company will have same amount of cleaning agents to all octane gas. As for recommended and required, my manual do say the same like nismopdb, but it only for optimal performance they recommended 91 or higher, not required. And it say maximum performance on unleaded fuel and again not premium unleaded fuel. It didn't mention anything that say using octane rating lower than 91 will cost damage (my sti manual had mention). Only when the engine is knocking and need to try upgrade to higher octane. I used to drive a Camry v6 that recommend premium But I fill 87 for 10+ years never have a problem. So many people still mistaking higher octane number mean better fuel.
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