MRV99

I can't remember which board that I posted a response to this but I will chime in. I was on a project for 6 months which I had to drive to the same location in the same traffic conditions. The trip was about 46 miles each way. So I put the Octane rating to a test. I would drive 2 weeks on 87, then I would drive 2 weeks on 93. I did this for about 3 months. What I found out was the average cost that I spent on the the 87 fill ups vs. the 93 fill ups were about the same. I found that I got less mpg using 87 but spent less money at the pump. I got greater mpg using 93 but it cost more. In the end It cost me the same to run 87 over the long run as it cost me to run 93. I don't have the numbers in front of me but I believe that I had to fill up 1 more time using 87 compared to 93. so the $2 to $4 price difference was negated by the one extra fill up. This is based on an average of $40-$50 fill up cost.

To hopefully make the results fair i would run the car to about 15 MTE and found my self putting in close to 18 gallons every time.

My Conclusion was just fillup with 93 and forget about it. you will have more power when you need it and the fuel economy negates the price difference.