Not sure if its been posted before
Any time there's an increase in gas prices you'll often see news stories posing the question: "Is premium fuel worth the premium price?" After the "expert" gives his two cents, the reporter will often conclude thus: "There you have it-if your vehicle runs fine on regular, stop throwing your money away on premium!" The average consumer can easily be lulled to the conclusion that there are no benefits whatsoever from running gasoline that costs a premium price of 20 cents more per gallon. The logic experts use to justify their claims is straightforward: If you run 87 octane and your car doesn't knock or ping, you'll see no difference if you use 89 or 91 octane. There are also claims that if your vehicle is only designed to run on 87 octane, you could possibly encounter problems from using higher octane."
To test the "premium gasoline is a waste of money" theory, we borrowed an unmodified Jetta 2.5L designed to run on 87 octane. In order to get a more accurate read on performance and pick up on any drivability differences, we decided to do more than just dyno tests. We performed the various tests using four tanks of gasoline. Under real-world driving conditions, the tank was run from full to empty first on 87, then on 91, and then back to 87. With the last remnants of 87 the car was dynoed until completely empty, then refilled with 91 and dynoed again.
• Increase of 1-2 mpg
• Increased throttle response and smoother power transitions
• Reduce risk of knocking or pinging
• Reduce risk of horsepower loss from heat soak
• $0.20 per gallon price premium