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MNBoxster · 04-23-2007, 07:19 AM

Hi,

All refined Gasoline contains the same amount of energy - approx. 114,132 btu/gal. The measure of octane is only a measure of the Fuel's ability to resist spontaneous combustion. It is NOT a measure of the Fuel's energy or power.

Back in World War I, Aviators had a problem, many engines would suddenly self destruct through detonation, not good if you're up in the air. An engine might run fine on one batch of fuel, but blow holes in the pistons on the next batch. The fuels seemed the same, weighed the same and may have even come from the same factory.

The fuel companies tried to analyze and standardise the fuel, but were unable to weed out the bad batches. Therefore a standard test engine with a variable compression facility was built and the fuel to be tested run through it. This heavy duty, single cylinder engine would be warmed to a standard temperature and at a set rpm the compression increased until engine knock occurred. This would give its Highest Usable Compression Ratio (HUCR).

But with time it was discovered that different labs gave different results. So in an attempt to produce an unvarying standard, two reference fuels were chosen. The high reference was 2-2-4 trimethylpentane (iso-octane), rated at 100 Octane. The low reference was normal heptane (n-heptane), rated at 0 Octane. Once the HUCR was determined, a mix of these to fuels was made up that exactly produced the same results as the HUCR test. The result is quoted as the percentage of iso-octane. Hence a fuel that detonated the same as a mix of 90% iso-octane and 10% n-heptane is called a 90 octane fuel.

The Octane Rating of Gasoline can be determined in 2 ways. Research Octane Number (RON) and Motor Octane Number (MON).

MON is always significantly lower than the RON.

The Research Octane Number Method, or "RON", is done on a standard test engine in a lab. The air temperature is controlled on this to a strict 125° F. Mild loads are put on the engine, approximating the loads you might put on your family car under normal driving conditions. This is called an F1 test.

The Motor Octane Number Method or "MON", uses standard test engine on a dyno which can alter it's load, and the air is introduced into the inlet at 300° F. Heavy loads, similar to full-throttle acceleration, passing on uphills, etc. are dialed into the engine. This is called the F2 test.

In each of these tests, an engineer notes ping and detonation at certain load conditions. This is then compared to two components of Gasoline - Isooctane (C8C18) a high value reference fuel. It has a knock resistance value of 100 RON, and N-heptane (C7C16) is a low value reference fuel. It is very prone to knock and has a value for 0 RON. The octane rating is determined by the fuel's ability to control the detonation against these reference fuels.

In most of the World, the RON method of determining the octane rating is used. In the US, we use the Pump Octane Number Method "PON" which is actually the average of the two - RON and MON (R+M/2). For example, if the F1 test showed 94 octane and the F2 test indicated 86, then the Pump Octane Number rating would be 90.

Now, so far as Octane Boosters are concerned, these are generally a waste of money. Most octane boosters are nitrogen carriers. Common ingredients are Methanol, Isopropyl Alcohol, Naptha, Xylene, Toluene (Tyline), Benzine, Hexane, Nitro Benzine and Aniline. Using these in quantities of no more than 3oz./gal. will raise the fuel's octane rating, but only by 0.02 octane or so. Counter-intuitively, their efficacy actually drops beyond these concentrations.

As stated, Octane in itself does not add power - it's just a measurement. However, an engine that's run on fuel with a lower octane than what's needed will run hot, detonate, and eventually lose power. The proper octane level will let the engine run to its full potential, but won't transform it into something special!

There are negative side effects to using Octane Boosters as well. They will attack plastics, rubbers and some fiberglass. They can discolor and attack most paints. Fuel filters will deteriorate if used with a booster-carrying gasoline. Also, some oils are affected by octane boosters. They can also make an engine run rich. Most are toxic to the skin, and the fumes can make you sick. Exposure to air can cause a 50-percent breakdown in their effectiveness and Ultraviolet rays will make octane boosters deteriorate. They will attack gas tank sealants and could plug up your entire fuel system if used together.

Add to this that most Octane Boosters actually cost on the order of some $80+/gal. (all for only some 0.02 Octane increase) when sold in consumer-sized packaging, and there's really no practical benefit to using them. 98 RON Fuel is equivalent to approx. 90 MON, or 94 PON and more than adequate for the engine to achieve it's peak performance. Hope this helps...

Happy Motoring!... Jim'99

04-23-2007, 07:19 AM	#3
MNBoxster Registered User Join Date: Sep 2005 Location: Minneapolis/St. Paul, Minnesota, USA Posts: 3,308	Hi, All refined Gasoline contains the same amount of energy - approx. 114,132 btu/gal. The measure of octane is only a measure of the Fuel's ability to resist spontaneous combustion. It is NOT a measure of the Fuel's energy or power. Back in World War I, Aviators had a problem, many engines would suddenly self destruct through detonation, not good if you're up in the air. An engine might run fine on one batch of fuel, but blow holes in the pistons on the next batch. The fuels seemed the same, weighed the same and may have even come from the same factory. The fuel companies tried to analyze and standardise the fuel, but were unable to weed out the bad batches. Therefore a standard test engine with a variable compression facility was built and the fuel to be tested run through it. This heavy duty, single cylinder engine would be warmed to a standard temperature and at a set rpm the compression increased until engine knock occurred. This would give its Highest Usable Compression Ratio (HUCR). But with time it was discovered that different labs gave different results. So in an attempt to produce an unvarying standard, two reference fuels were chosen. The high reference was 2-2-4 trimethylpentane (iso-octane), rated at 100 Octane. The low reference was normal heptane (n-heptane), rated at 0 Octane. Once the HUCR was determined, a mix of these to fuels was made up that exactly produced the same results as the HUCR test. The result is quoted as the percentage of iso-octane. Hence a fuel that detonated the same as a mix of 90% iso-octane and 10% n-heptane is called a 90 octane fuel. The Octane Rating of Gasoline can be determined in 2 ways. Research Octane Number (RON) and Motor Octane Number (MON). MON is always significantly lower than the RON. The Research Octane Number Method, or "RON", is done on a standard test engine in a lab. The air temperature is controlled on this to a strict 125° F. Mild loads are put on the engine, approximating the loads you might put on your family car under normal driving conditions. This is called an F1 test. The Motor Octane Number Method or "MON", uses standard test engine on a dyno which can alter it's load, and the air is introduced into the inlet at 300° F. Heavy loads, similar to full-throttle acceleration, passing on uphills, etc. are dialed into the engine. This is called the F2 test. In each of these tests, an engineer notes ping and detonation at certain load conditions. This is then compared to two components of Gasoline - Isooctane (C8C18) a high value reference fuel. It has a knock resistance value of 100 RON, and N-heptane (C7C16) is a low value reference fuel. It is very prone to knock and has a value for 0 RON. The octane rating is determined by the fuel's ability to control the detonation against these reference fuels. In most of the World, the RON method of determining the octane rating is used. In the US, we use the Pump Octane Number Method "PON" which is actually the average of the two - RON and MON (R+M/2). For example, if the F1 test showed 94 octane and the F2 test indicated 86, then the Pump Octane Number rating would be 90. Now, so far as Octane Boosters are concerned, these are generally a waste of money. Most octane boosters are nitrogen carriers. Common ingredients are Methanol, Isopropyl Alcohol, Naptha, Xylene, Toluene (Tyline), Benzine, Hexane, Nitro Benzine and Aniline. Using these in quantities of no more than 3oz./gal. will raise the fuel's octane rating, but only by 0.02 octane or so. Counter-intuitively, their efficacy actually drops beyond these concentrations. As stated, Octane in itself does not add power - it's just a measurement. However, an engine that's run on fuel with a lower octane than what's needed will run hot, detonate, and eventually lose power. The proper octane level will let the engine run to its full potential, but won't transform it into something special! There are negative side effects to using Octane Boosters as well. They will attack plastics, rubbers and some fiberglass. They can discolor and attack most paints. Fuel filters will deteriorate if used with a booster-carrying gasoline. Also, some oils are affected by octane boosters. They can also make an engine run rich. Most are toxic to the skin, and the fumes can make you sick. Exposure to air can cause a 50-percent breakdown in their effectiveness and Ultraviolet rays will make octane boosters deteriorate. They will attack gas tank sealants and could plug up your entire fuel system if used together. Add to this that most Octane Boosters actually cost on the order of some $80+/gal. (all for only some 0.02 Octane increase) when sold in consumer-sized packaging, and there's really no practical benefit to using them. 98 RON Fuel is equivalent to approx. 90 MON, or 94 PON and more than adequate for the engine to achieve it's peak performance. Hope this helps... Happy Motoring!... Jim'99 Last edited by MNBoxster; 04-23-2007 at 01:59 PM.