funny stuff here.......i've began to see better mpg's with 87 octane. I only buy brand name gas as well.
anyhow, here goes.......Stock 2015 Ram CC Sport, 6'4 bed, 4x4 with 3.92 gears and a flowmaster 50 series bolt on.
I've been working on a little experiment for the last month and half. I take two trips a week ( one is about 80 miles round trip, 90% highway ) and another ( about 65 miles round trip ( almost 95% highway ).
I ran 89 octane for the last 6-8 months, so the truck was used to having the 89 octane in there. With cruise control on 70 mph for almost 95% of the time ( mainly on the highway ) and me driving somewhat gingerly when i had to get off the highway to get to my destination ( about 2-3 miles ) i would average about 19 mpg. Some times the trips total mpg would be as low as 18.6 and others i've have it up to about 19.3. Obviously head winds, outside temps and other factors played their parts, so there are going to be various
Now, for the last month or so I have switched back to 87 octane. While I do think the truck seems to be slightly less responsive ( possibly placebo, but i cant really measure, so i will just stick with my butt dyno ), I see that my mpg may have actually gone up with 87. I have made 2 trips on each of my variations ( so 4 total ). Not once have i dipped below 19.2 mpg and my most recent one actually had me at 20.0 mpg and one at 19.7.
For this experiment, I got my truck up to 70 mph and hit cruise control at the exact same starting point on the highway and reset my trip meter ( which also calculates mpg for that trip ) and then I checked my overall trips mpg at the same point as i came near the end of my trip ( same point that i turned the cruise control on ) on the highway.
For my miles off the highway, i made sure to drive the same way ( as best i could ) each and every time to keep the test as accurate as possible.
Next test will be to add my oil catch can and see if the elimination of the misty oil vapors ( which lower octane ratings ) makes a difference either way. My theory, i can run 87 octane and have something closer to 89, without paying 25-30 cents a gallon more for it. If the mpg's go down, so be it, if its more responsive, than great.