LogFAQs > #979718201

I hope people here realize that if your car says regular 87-octane is good, you get no benefit in adding mid (89) or premium (91-94) octane. But if your car says it needs mid or premium, you better put mid or premium, otherwise your car engine might start to knock and cause more issues.

One of my cars says 89 is preferred, but 87 is also acceptable; the manual says you can expect less power and less efficiency with 87, and I actually see this difference when I drive it. And since I get gas at Costco, where mid is unavailable, I put premium in that one (premium at Costco costs less than mid at normal gas stations anyway). All other cars I own currently requires only 87, so 87 it is.