O.k....my turn!
This thread originated in August, so it’s good to see that an old thread can generate new life and vigor in our members. I love it when a thread gets hot!...What fun. Now, this is it, the part where I not only throw in my 2 cents but I get to go do some homework before I throw it in there!.........I like to find the facts for us all to chew on.
Your correct Karl. If you look on the side of the fuel pump, you'll notice a sticker from the agency who did the sample and the date it was done. It's required by law. I too have fuel testing experience. I was the "oil king" on board a US Navy destroyer where I was responsible in the inventory, control and testing of 278,000 gallons of diesel fuel.
The below material is reference from the Louisiana State Governments web site, training on fuel octane. I hope it sheds some light on the octane rating for ya’ll. I thought it was pretty interesting. You’ll notice that diesel doesn’t have an octane rating, it’s rated in cetane.
Fuel octane requirements for gasoline engines vary with the compression ratio of the engine; diesel cetane requirements also vary with the compression ratio. Engine compression ratio is the relative volume of a cylinder from the bottom most position of the piston's stroke to the top most position of the piston's stroke. The higher an engine's compression ratio, the greater the amount of heat generated in the cylinder during the compression stroke.
Posted octane numbers on gasoline pumps are a result of testing fuel performance under laboratory and actual operating conditions. The higher the octane rating on fuel the less volatile (evaporative qualities) and the slower the fuel burns. Higher octane fuel contains more POTENTIAL energy but requires the higher heat generated by higher compression ratio engines to properly condition the fuel to RELEASE that higher potential energy. In the refining process, fewer gallons of higher octane fuels are yielded from a barrel of raw crude.
If fuel octane is too low for a given compression ratio, the fuel prematurely and spontaneously ignites too early and the fuel charge EXPLODES rather than BURNS resulting in incomplete combustion. The net effect is a loss in power and possible engine damage. The operator hears an audible "knock" or "ping", referred to as detonation. Detonation may vary from a faint noise on light acceleration to a constant, deep hammering noise while driving at a constant speed. Improper timing adjustments, vacuum leaks, or excessively lean fuel mixtures may also cause detonation.
Many vehicle owners believe that higher octane fuels are better for their vehicles since they are labeled "PREMIUM." The logic is that since it is a premium fuel it must be better. In reality, the premium label originates from the higher cost to refine and the resultant higher retail cost. Some refiners label their high octane fuels "SUPER." Some owners think that these fuels will make their vehicles more powerful. Only engines with high compression ratios can deliver all the potential energy from higher octane fuels! Always consult the manufacturer's octane recommendation to determine the proper octane requirements for any given vehicle. Generally, engines with compression ratios of 9.3 : 1 or less will safely operate with unleaded 87 octane fuel. Engines with higher compression ratios usually require higher octane fuels.
Many owners who operate vehicles designed to operate on 87 octane fuel experience ping and knock. They usually "fix" this problem by purchasing the higher priced, higher octane fuels. Most owner's manuals indicate that some light and intermittent ping is normal but that heavy or sustained ping or knock should be attended to by either purchasing the correct octane fuel or servicing the engine.
Most fuel refiners blend fuels for geographic areas and adjust their blends seasonally. These blending techniques compensate for the decrease in oxygen content with an increase in altitude and compensate for volatility during the warmer or cooler seasons. Significant ambient temperature changes (40 degrees Fahrenheit) or altitude changes (4,000 feet) may cause some serious engine detonation. This problem is usually corrected by filling the tank with "local" fuel that has been properly blended for season and altitude.
