Just make sure everyone is aware of the difference between the RS and RT. The RT does run a higher compression ratio than that of the GS/RS and that is why BRP recomends higher octain for the RT. The RT is 12.2:1 and the RS is 10.8:1. Octain slows burn rate and is harder to ignite, compression increases burn rate and makes fuel easier to ignite. Lower compression will run better on lower octain and higher compression will run better on higher octain. There are some very complicated mathmatical formulas for all of this. The objet is to get the fuel ignition point at the desired piston location and the burn duration for a desired length of piston stroke. High compression and high outdoor temps mixed with city stop and go traffic is a bad mix for high compressin engines (12.2:1). If your engine pre-detinates you may not really know just how much but trust me your engine does.
Fact, high octain fuel in a low compression engine is a waste of $ and will probably rob HP. What happens is the burn rate slows to a point where the fuel does not all burn through the desired piston range. This is not the desired condition. By the way low is in the 8`s, low 9`s.
Fact, low octain fuel in a high compression engine does not create max efficiency. The higher compression causes fuel to burn faster (faster flash rate) so the fuel will be all used up before the desired piston range has completed leaving a dead zone in the stroke. High comp. at least in my oppinion is about 12.5:1 and above. 10.8:1 is somewhere in the middle so no you probably can not tell one grade from another. If you have an RT as some of you have noticed, you should be able to tell 87 from 93. Right now it is cool so not as big of a deal. This summer when it is hot as @#$% it is a bigger deal.
Just incase some may not know why low octain is so bad for high compression here is a short explanation. All modern engines ignite fuel before the piston reaches full compression or the top of the stroke (TDC) so that the max flash point can occur just as the piston starts its down stroke. If you use fuels that flash to fast you will reach this peak before the piston is at the top of its stroke. This wastes some of the fuels efficiency and literally tries to shove the piston backwards (pre-ignition).
There is way more to this but I made it as simple as I could. Bottom line BRP makes the recomendation for higher octain in the RT for a reason, not just to suck $ out of your pocket. Hope this helps.
PS: I know my spelling is bad but hope it`s not so bad you couldn`t read it.
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