Good point. I did think about the summer/winter blend. I didn't consider it much since I used both during the Spring and weather here in Cali is consistently mild this time of year. I switched back to Shell in the past month (beginning of April). Since I commute a lot, I get gas rather frequently. The change in mpg was noticeable on the first tank after switching, which I thought was just my imagination, but it has been consistently 36-38 mpg since I switched back to Shell in April. Prior to April, 40+ mpg consistently using 76. Not a big deal I guess, just found it interesting enough to google the topic and find this thread lol
Shell offers much better reward incentives (discounts, etc) than 76 does, which is why I gave them another shot to reduce fuel costs. But over time it probably balances out the same.