I have heard guys on the Jeep forum board that are getting 2-3 mpg better with 87
This doesn't make sense. Some vehicles (hemi) MAY get better mpg with the 89 octane, but NO VEHICLE will get better mpg with a lower octane. A higher octane will give you the same mpg or maybe better depending on timing advance and compression ratio mainly.
Also, where I live (Orlando)....and I assume everywhere operates similar to this....all fuel comes from the same place....for me it's the central florida pipeline, and each company drops X volumes of their "special" additives in the truck, and drives off.....basically all fuel is the same, and in my opinion all these additives are all the same as lucas fuel injector cleaner or similar....I've run my truck on shell, hess, sunoco....etc for higher prices, and at the cheapest place called "gas town" that doesn't even have a credit card machine on the pump, and my truck runs the same(proven at the drag strip)...I run 93 octane always with the 93 SC tune...but I also use my own additives....I run seafoam about every 50k miles and marvel mystery oil every X tankfuls (maybe 4-8 tankfuls). I like to think the seafoam keeps the fuel system/injectors clean, and the MMO lubricates the pump and the rest of the fuel system (newer fuels have very few lubracants as compared to older fuels).... who knows, the seafoam and MMO may do nothing lol.