I have found a station that sells non ethanol gas with a 93 octane rating. The Spyder sure runs better on a tank of this stuff, but I am not sure if it is the non ethanol or the higher octane that makes the difference. The gas filter probably also needs changed, so that may be a factor also. Will post after changing filter and alternating a few tanks of ethanol/non ethanol gas. I did not notice any difference in mpg, but it definitively was more responsive when accelerating.
By volume, ethanol has 20% less energy than gasoline. It's the ethanol, or lack of ethanol, you are noticing, not the octane. As I understand octane, the higher rating decreases the likelihood of unintentional detonation of the air/fuel mixture in the combustion chamber. In other words, it reduces the volatility of the fuel so it won't burn as easily. Octane adds no 'power' to the fuel, but does make the fuel more stable when used in higher compression motors, like the RT uses.
Here is some interesting information on octane I found online:
The
octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes
knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the
horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.
The name "octane" comes from the following fact: When you take crude oil and "crack" it in a
refinery, you end up getting
hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of
methane, propane and butane. All three of them are
hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has
eight carbons chained together.
It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.