[JimD]

Chris,

I can see where a tuned car needs more octane. I'm also willing to accept that an untuned 128 needs more octane if it's driven hard. That's why I put higher octane in mine for the occasional autocross. I just don't think it pays for itself in mine for my daily commute.

Shell isn't more expensive for me, however. Around here, RaceTrak is the better deal for higher octane. But for 87, my rewards car 5 cent discount makes Shell close and sometimes lower than Walmart (don't have a Costco nearby). I guess it's a regional thing. Racetrak is well priced for regular and then only goes up 10 cents for mid and another 10 for premium. Shell often increases 15 or 20 cents as you go up in grade. I don't remember for sure but i think Walmart around here increases like Shell.

The other comment I have on use of Costco or Walmart gas is there is a significant believe that the upper tier gas brands have benefits due to better additive packages. I don't remember seeing data to back up that belief. I don't think the occasional fillup with other gas hurts my car, I think it might even help, but when I can get the Shell BMW recommends for the same price or less than the "off-brand" gas, I think it's a good option. But in other vehicles I've always used whatever was cheapest. My son gets my "hand-me-downs" and has one with 250K miles that runs fine and another with 150K that will probably give him close to another 10 years of reliable service. Can't cause any big problems. If he needs to clean out carbon, sometimes he uses seafoam in the intake.