octane

2014 Mazda 6 - 58k miles Been using regular 87 octane since I got the car. Yesterday I was distracted when pumping gas and filled with 91. Seems peppier. Is it just in my head?? Anyone notice a difference in performance when using a higher octane gas? Any downside if I continue using 91?

The owner's manual calls for gasoline with an octane rating of 87 or higher. The engine (1.5L) has a pretty high static compression ratio of 10:1. I'm wondering if using a higher octane gas would provide a boost in performance/fuel economy, or be better on the engine in general? I know that...

I have a 2007 Miata MX-5. The owner's manual says to use 95 octane fuel. My previous 1999 MX-5 had no such requirement. Does this engine really need the higher grade gas? Has anyone used 87 octane routinely and found a difference? Thanks. Jim