rdharper

Unless you've measured the difference with your own vehicle, I'd not assume you will do better with premium either with efficiency or performance. Remember their is more energy per unit volume in the lower octane gas.

With current design, your vehicle will probably be able to take advantage of the lower octane. This is because the range of settings available to the ECU is such that the ignition (for instance) can be advanced to handle the lower octane gas, with no penalty.

The fact that the owners manual might state "high octane required" is patently not a fact, but a result of factors having nothing to do with your vehicle, mainly the excellent engine of capitalism taking advantage of the ignorance of the consumer.

TRunner

You might be right, but for now I listen to my vehicle and the gas cap. I did try one tank of regular grade and my milage and "umph" fell. It also didn't quite sound right. Seemed to be idleing a bit low and rougher. I never heard the tell tale knocking, but who knows. I am happy with the results of running the suggested premium.

Not to mention I am one biased SOB... I work in one of those major oil companies and will gladly pay higher prices for my gas. It makes me work more and get paid a lot more!!!