MTI - 10/9/2004 3:40 PM
Again,the assumption that the anti-knock sensor will activate isn't necessarily so. I do agree that if it does, the change in tuning will affect mpg and performance, but the only way to verify that the sensor is kicking in is to check the before and after mpg and performance. If there is no change, then there's no reason to use the premium fuel.
MTI, yes, if the fuel did not predetonate, i.e. under pressure, then it would be ok. The whole reason the manufacturer specifies the minimum octane rating is to avoid predetonation. There appears to be enough information from posts in the various BenzWorld fora -basically by folks who did your experiment intentionally or unintentionally - that indicates that the minimum octane rating is not over specified. If we can trust those other posts, we might also look at the compression ratio is an indication.
Teky, I know you know this but for those who don't, and might be confused by it, let's clarify why you state higher octane numbers. The original question was from someone in NA where the PON, Pump Octane Number, is (R+M)/2 not RON like in the UK. The R is RON or Research Octane Number. RON is almost always higher than MON, Motor Octane Number. RON is measured under more gentle conditions than MON. While RON is higher than MON or (R+M)/2 and might sound more impressive, it really is the same as the higher octane rated fuels in NA. One catch though. RON is not a good indicator of fuel stability. That low stability means that the fuel may behave like a lower octane when put under stress. MON is a better indicator of stability. While fuels in the UK might be regulated well enough for RON to be safe, this might not be true for other regions that use RON, making 98 RON attactive.
tiggerfink, I think one of the posts I was referring to was from you. Good story. One thing, an octane booster could be 100 octane fuel - iso-octane- or other higher octane fuel. While you would be adding it to your fuel, it really is just a higer octane gasoline and would be fine to add. Even if you added too much, all you would have is a higher than needed octane and that is ok.
benztech1209, absolutely [:D]. In fact, if you use the lower octane fuel, the fuel efficiency hit makes the delta even less than that. If you didn't check out the link I posted above, I had an example you might get a kick out it since it is on the same track as your post. (MTI, by the way, in that example, I used an estimated average of reported numbers from 3 or 4 individuals who posted their hit in fuel economy when using one grade below spec'd for the R170. Your mileage may vary[:o)]... I'm sorry, I couldn't help it.)