I talked to a mechanic ( non - nissan ) who told me that a person should run as low octane as they can with out pinging because the lower flash point will give better performance and MPG.I can see that it would burn more efficiently and give better MPG, but under hard exceleration, wouldn't the knock sensors retard timing and give worse performance?

Excellent article here addressing your query.

You're right, good article.Since I typically open it up at least every other day, I guess I'll stick with premium.