TheDr9669
Registered Member
Three days ago I made a small detour on my way home from out of town to snag me some ethanol free fuel. I had been looking for this supposedly mythical elixir for a while and finally found a source. I was disappointed to find out that it was only regular 87 octane, but figured that I was already there and filled up. I noticed a very big difference in the car by the time I got back on the freeway. The ECU remapped for the lower octane fuel very quickly. My R-Spec feels way slower than my previous '11 4.6 on a bad day. With the intake and exhaust mods on the car I can hear that the timing has been drastically been pulled back and the cam phasing does not advance nearly as much, if at all any more. It is a night and day difference. I think my car went from a 13.3 second 1/4 to 14+ seconds. (Butt dyno)
On the flip side, the car runs & idles much smoother, and starts easier. Overall the engine feels "nicer" and is quieter. (Quieter due to the cam phasing being held back and the very noticeable difference of the intake sound.) I might be getting .25-.5 mpg better overall, but I think it is more likely because I am not squeezing the go pedal as much due to the lack of sound.
If I can find ethanol free 91+ octane fuel I will try this experiment again. In the mean time I would recommend that for the 5.0 do not use anything less than the recommended 91+ octane; The difference in performance is drastic. Now I have to burn the other half of this tank so I can put the good stuff back in.
On the flip side, the car runs & idles much smoother, and starts easier. Overall the engine feels "nicer" and is quieter. (Quieter due to the cam phasing being held back and the very noticeable difference of the intake sound.) I might be getting .25-.5 mpg better overall, but I think it is more likely because I am not squeezing the go pedal as much due to the lack of sound.
If I can find ethanol free 91+ octane fuel I will try this experiment again. In the mean time I would recommend that for the 5.0 do not use anything less than the recommended 91+ octane; The difference in performance is drastic. Now I have to burn the other half of this tank so I can put the good stuff back in.
