OK, since this turned into a fuel and octane thread, I'll take the bait.
There is not a fuel composition sensor on the Raptor. It can not adjust for octane. It can only retard the timing when it senses knock. So the comment made by Grizz about ecu needs time to adjust is just stupid.
Under the right circumstances, it is true that increasing the octane will have no benefit. Most of the time you will see a benefit because these trucks are tuned to run off the knock sensor. So the higher octane will keep it from retarding the ignition timing. Running octane above the point where the knock sensor is no longer retarding the timing in theory actually produces less power and worse mileage. For an extreme example, go blow some coin on 110 octane and test it out for yourself. Race engine builders don't just run 110 octane. They dyno an engine with the lowest octane that doesn't cause knock. 106 octane and no knock is more power than 110 octane and 104 octane might blow the engine. You can apply these same principles to the Raptor octane discussion.
---------- Post added at 09:00 PM ---------- Previous post was at 08:47 PM ----------
Most vehicles rated to run E85 (obviously not Raptors or Ecoboosts) will have a fuel composition sensor. This sensor acts like a switch, on or off, not an analog signal like a rheostat. So if the sensor detects E85 it activates and the ECU can advance the timing to take advantage of the higher octane of the E85.
