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Old 02-13-2007, 08:22 AM   #1
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The Mystery of 'Octane' Finally Uncovered

**Originally posted on SuperchargersOnline.com**

The Mystery of 'Octane' Finally Uncovered

What is octane? The concept of octane is peculiar to many people, including myself. I can't see it, I can't hold it, I can't buy it by itself, but I know I know I pay extra for it if I want more than 87 of it in my gas. Today we take an in-depth look at what octane is, and what significance a gasoline's octane rating has with regards to a supercharged engine.

The Simple Definition

An octane rating (87 vs. 89 vs 92, etc.) is a measure of a gasoline's ability to resist detonation, which manifests itself in a pinging or "knocking" noise. Higher numbers indicate that the fuel can be compressed to a higher level before detonation / knock occurs in an engine, which occurs when. As described in "Detonation, Knock, and Pre-Ignition 101", detonation / knock occurs when air and fuel that is ahead of the combustion flame front ignites before the flame front arrives.

The Complicated Definition

Octane is actually more than just a rating - it is a hydrocarbon just like methane (single carbon atom), propane (three carbon atoms), butane (five carbon atoms), and heptane (seven carbon atoms). Octane (C8H18) is a hydrocarbon with eight carbon atoms and eighteen hydrogen atoms. 100% octane fuel is remarkably resilient to compression (i.e. it does not combust when compressed) and is thus resilient to detonation / knock. This resilience is derived from the branching of octane's carbon chain (see figure). Because of the nature of octane as being resilient to detonation, all fuels are compared to 100% octane as a benchmark fuel, from which an "octane rating"can be obtained. Heptane, a hydrocarbon with seven carbon atoms, compresses very poorly and spontaneously combusts even under small amounts of compression. In other words, Heptane's behavior when compressed is diametrically opposed to Octane's behavior under the same conditions. For this reason, Heptane (which has an octane rating of zero) is the other benchmark fuel used in the octane rating system to determine a fuel's octane rating. A fuel that spontaneously combusts (knocks) under the same amount of compression as a fuel composed of 87% octane and 13% Heptane would have an octane rating of 87. This is not to say that 87 octane gasoline is made up of 87% octane and 13% heptane, rather that the 87 octane gasoline "knocks" in a laboratory knock engine at the same compression ratio as a fuel composed of 87% octane and 13% heptane.

The coomposition of an octane hydrocarbon.

Unfortunately, it gets even more complicated. Because various fuels respond differently under varying engine loads, a gasoline may get a different octane rating on a free running engine and one under load. For this reason, the octane rating label that we see at the pump (monitored by the U.S. Cost of Living Council) is actually an average of two octane ratings - the motor method rating (where the engine is run under a load) and a research method rating (where the engine is run freely). The formula used to get the CLC Octane number on gas pumps in the United States is thus: (Motor Octane Number + Research Octane Number) / 2.

What's the benefit of higher octane?

Higher octane fuel has only one beneficial feature - it allows an engine to run at higher temperatures with more advanced ignition timing under higher levels of compression witout detonating / knocking. Higher octane fuel does NOT have more potential energy and will not make an engine perform better unless that engine is knocking. On modern engines with knock sensors, higher octane fuel may make the engine run better if the knock sensors are retarding the ignition timing, which hinders performance. High octane fuel does not burn cleaner, it does not clean your engine, it does not increase horsepower or torque (unless you are experiencing knock), it does not smell better, it does not increase fuel economy (unless you are experiencing knock) and is not better for the environment. If you buy higher octane fuels for any of the above reasons, STOP!

When should I switch to a higher octane fuel?

First off, never run lower octane fuel than is recommended by the vehicle's manufacturer. If the vehicle manufacturer recommends 89 octane gasoline, this means that the engine has been tuned to perform optimally without detonation on 89 octane fuel. Once you've done some modifications to your engine, the manufacturer's recommended gasoline may no longer suffice. Obviously, if you can hear detonation inside your engine in the form of pinging or "knocking", try a higher octane fuel. You will also need to run a premium grade fuel (91+ octane) if you have a supercharger, turbocharger, or if you have an ignition programmer that advances your ignition timing.

Why is higher octane fuel more expensive?

Higher octane fuels are more expensive because they must go through more refining steps that increases the octane rating. These additional steps do not make the fuel better in any other way.

How is it possible to have 100+ octane gasoline?

There are some fuels that are even more resilient to compression than 100% octane. Some additives, like tetraethyl lead, increase the gasoline's ability to operate without knock. Some racing and airplane fuels have octane ratings of 110+!

Last edited by SilentNoise; 02-13-2007 at 09:21 AM.
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Old 05-06-2010, 10:12 AM   #2
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Re: The Mystery of 'Octane' Finally Uncovered

Ripped from another board:

Octane boosting...

Octane boosters are popular in the performance scene because they often regain power last through detonation. Sold for around $25 in a handy bottle, they’re a convenient fuel additive and horsepower helper. But with so much brands on the market, you may be fooled into thinking they’re all as effective as each other. Which they’re not! Differing chemical compounds, additives and even volumes, mixed in with a good percentage of advertising, ‘independent" testing and testimonials all conspire to confuse the consumer away from the single most important paint: does it improve the octane rating?

Let’s see what’s worth it in octane boosters.


The boys at "The Macquarie Library" describe detonation as: "Excessively rapid burning of the fuel mixture, often caused by auto-ignition due to excessive temperatures in the combustion chamber, incorrect ignition timing, lean mixtures, too high a compression ratio or unsuitable fuel," – as in too-low an octane rating.

Heard as a faint, metallic rattle, detonation is accompanied by a loss of power and can cause serious damage to piston crowns.

The significance of detonation is such that many companies produce fuel additives designed to increase the inherent octane rating of a given fuel. The proliferation of octane boosters has in part come about in recent times thanks to low quality Australian fuels. White or "Super" leaded fuel has been reduced from 98 to 95-96 octane, Premium Unleaded has also dropped to a minimum of 95 octane. And this presents a problem for high-performance cars designed to run on higher octane European or 100 octane Japanese fuel. Japanese import performance cars, Subaru’s STI WRX for example, runs an ECU program for 100 octane, but sometimes detonates on our Australian PULP.

All engines are different though and with Honda’s S2000 2.0-litre engine running a high 11.0:1 compression ratio, it relies on advanced engine management as much as quality fuel. But it can sustain its power on PULP. And of course any turbo owner who has experimented with boost will know if you run too much, it will detonate, so improving the octane is vital for maximum performance.

We must state that unless an engine is detonation through low RON fuel, octane boosters have little use. However, in a turbo or high compression application, the inclusion of a better grade of fuel allows the engine management system to optimize ignition timing and fueling.


For this test we tracked down nine different makes and models of octane boosters, two fuel "additive," a straight race fuel and a drum of Toluene. Where there were several different "levels" of octane boosters in the one brand, we chose the strongest version.

The biggest claims the bottles have is the amount of "points" they claim to increase. This is ambiguous as a "point" can relate to either 1.0 RON (Research Octane Number) octane points, or 0.1RON octane points.

The list of entrants in our octane Olympics included:

STP Octane Booster
Wynns Octane 10+ Power Booster,
Amsoil Series 2000 Octane Boost,
Super 104+ Octane Booster,
VP C5 Fuel Additive,
ELF HTX 330 Racing Fuel Stabilizer,
Nulon Pro Strength Octane Booster,
PowerFuel Super Street Nitro Based,
PowerFuel Max Race Nitro Based,
NF Octane Booster Racing Formula,
NOS Octane Booster Racing Formula,
VP Motorsport 103 Unleaded Racing Fuel


To conduct these tests we contracted independent laboratory Intertek Testing Services, who would test our products on a knock engine.

We had to also find a base fuel to add our boosters to so we went to the closest public petrol station, a Shell on the outward-bound side of the Westgate Bridge in Melbourne.

Being a performance-based test, we chose premium unleaded fuel as this represents the most common high performance fuel (ie: if you start with regular unleaded, you’re wasting money!). We should add that "some" boosters would have improved the octane rating of regular unleaded proportionately more than our tests with PULP.

With a RON rating at a minimum of 95, we first established the exact octane of the PULP. The biggest surprise was our randomly select Shell resulted in a quite high 96-8 RON.

We precisely measured and mixed each additive to the PULP, according to each manufacturer’s recommendations and specs and poured each into the knock engine’s tank. The compression ratio was then slowly increased until it started to knock, gaining a threshold of detonation and subsequently a maximum RON rating.

Of less importance but still worth mentioning is the design of the bottles: since most people will be pouring it straight into a tank, the design of a bottle is important to prevent any spillage on paintwork causing damage.

So let’s look at the results!



Octane points

It’s very easy to confuse octane ratings as there are a number of separate international standards. MON (Motor Octane Number) is the number derived from a fuel when it’s applied to a test engine run at 3000rpm rather than 600rpm and higher inlet temps and ignition advance. The Australian importer of 104+, Andrew Holdsworth, suggested MON is seen as a more real-world test.

Though none of the fuel companies promote the MON figure which is normally between 7 and 10 numbers less than RON (Research Octane Number).

Intertek’s Graeme Marks believes RON provides the general public with an idea of which additive works more effectively. And being the most commonly-used reference, we’ve used RON for all our tests.


PowerFuel Super Street Nitro Based

946ml treats 35 litres RRP: $35

Right from the start, we were told PowerFuel’s additives weren’t necessarily octane boosters, but horsepower helpers. We kept this in mind when testing both the products, but of the two only the Super Street claimed it was specifically designed to increase the octane rating of PULP. With a 20-percent nitro mix, Super Street Nitro-Based still improved octane ever so slightly (0.2RON) but the real test for these two would come on the dyno runs.



PowerFuel MaxRace Nitro Based

946ml treats 35 litres RRP: $45

Containing another 15 percent more nitromethane than the SuperStreet formula, MaxRace doesn’t claim to increase octane, but the verbal recommendation was the same, ie: its main characteristic is to boost horsepower, not octane. For a fair comparison of these two additives, you need to look at the power they produce. As for octane, it proved very similar toe the SuperStreet formula bumping up octane ever so slightly.



STP Octane Booster

350ml treats 57 litres RRP: $10.95

One of the cheapest of the group, the STP was also one of the hardest to find. Auto stores either didn’t stock it, or had simply run out! Claiming to increase the octane 2-5 points, in a well-designed-for-pouring bottle, the STP – used in the ratio determined by the label - improved the octane marginally by just over half a point. A little disappointing unless you interpret STP’s claim actually meant 0.2-0.5 points. Then it’s a good result!



Wynns Octane 10+ Power Booster

325ml treats 60 litres RRP: $10

The Wynns was the cheapest of the lot and claimed an increase between two and five points, again not actually listing what a "point" related to. Strangely though the 10+ could indicate 1RON and if this is the case going by our tests it almost lived up to its name. It didn’t quite live up to its claims however, increasing the octane rating by 0.8RON.



Super 104+ Octane Boost

473ml treats 83 litres RRP: $25.95

The acknowledged winner of all previous testing in this country, Super 104+’s bottle stated we should expect an increase between four and seven point. With a new formula introduced about 12 months ago, identified by an "Eagle" logo on the back of the bottle, the Super 104+ seems to have lost its edge with a marginal gain of just less than 1.0RON.



VP Racing C5

355ml treats 75 litres RRP: $19.95

VP has a strong reputation with fuels and its high octane formulas are very popular (VP?) with drag racers. VP Racing’s C5 Fuel Additive lacked any indication of contents nor claims, but the C5 additive still provided a reasonable increase of 1.3RON.



NOS Octane Booster Racing Formula

355ml treats 60 litres RRP: $28

NOS, a relatively new octane booster, comes in "1/10th" scale bottles designed to emulate the actual nitrous bottles of its successful NOS systems. The Racing Formula is the strongest of three concentrates and containing Hydrotreated Aliphatics and Methylcyclopentadienyl Manganese Tricarbonyl (try saying that 10 times in a row), it contains a lead replacement which NOS claims increases the octane rating by as much as seven points. Obviously not recommended for street use, it also included with a handy pouring spout. In testing, it proved a good result improving the octane rating by almost 2RON

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Old 05-06-2010, 10:14 AM   #3
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Re: The Mystery of 'Octane' Finally Uncovered

2nd part:


ELF 330 Fuel Stabilizer

1000ml treats 50 litres RRP: $45

"If you spill it on your paintwork, don’t rub it off – rinse it with water" were our works of warning. We were also told to "pre-mix" the ELF before adding it in a fuel tank (which with this test we were doing anyway) as the ELF has a tendency to settle to the bottom of fuel if it’s either not mixed properly or left to sit. This was made somewhat more difficult by the design of the bottle, which tends to drip when pouring. With some nasty stuff known as Aniline, the ELF doesn’t claim any numbers, and provided a decent 1.8 RON point improvement.



Amsoil Series 2000 Octane Boost

354ml treats 57 litres RRP: $23

Recommended for off-road and racing use, the Amsoil Series 2000 claimed to increase the octane rating by up to seven points. It came up a little short, but still proved surprisingly good with a full 2.0RON improvement. And good enough for the bronze medal in our Octane Booster Olympics.



Toluene (Toluol)

20 litres treats 100 litres RRP: $48

Since toluene (pronounced toll-you-een – also known as methyl benzine) isn’t a commercially advertised octane booster. We were unsure of exactly what ratio to mix the clear Toluene to the fuel, with recommendations between 10 and 30 percent. From personal experience, we have seen high percentages increase octane even further, though 30 percent is considered the maximum. Available only from various fuel distributors (it is a special order through services stations), under advice we ran a 20 percent mix (quite a lot more than the others) and saw an impressive improvement of 2.5 RON, for the silver medal.



NF Octane Booster Racing Formula

250 ml treats 80 litres RRP: $29.95

Time for an Aussie-made product. From Perth, the NF Octane Booster Racing Formula was the smallest bottle in the field, but looking at the mixing ratio, also the strongest NF relies on an incredibly small dose – a mere 3 percent! Claiming to increase octane as much as 6.0 RON, NF took the gold medal in a surprising tie. If it were a split decision based on concentration though, it would be the clear winner.



Nulon Pro Strength Octane Booster

500 ml treats 60 litres RRP: $20.95

Note: Also available in four-litre container for $110

The Australian-made Nulon Pro Strength Octane Booster is the top of the range Nulon fuel product, claiming to boost octane "up to seven number". The Pro Strength gained a test-winning, gold-medal-gaining and Nf-equalling 2.8RON increase. And at $21, it’s good value too!


VP Motorsport 103 fuel

Used straight fuel (20-litre minimum) RRP: $70

Purely for interest, we decided to also test a straight racing fuel. While there are a number available (such as ELF) for no particular reason we chose VP. The highest octane VP fuel which was still totally street-legal was the Motorsport 103. Working out at $3.50 per litre and "designed for maximum power and throttle response", the VP was very impressive with an octane rating of 107RON – more than 10RON points more than PULP. Obviously more expensive than the boosters, if octane is problem, racing fuel like VP may be the answer.


As the name suggests, a knock engine is designed to test the detonation or anti-knock rating of fuels and fuel additives. It’s a slow revving engine capable of running most fossil fuels through an adjustable compression ratio. As the comp ratio increases, it accurately measures the intensity of the knock and determines the fuel’s octane rating.

The world standard is a one-cylinder two-valve four-stroke engine with exposed valve gear. Archaic in appearance, a carby is fed from any one of three fuel bowls to allow three different fuels to be run back to back. The mixture is actually controlled via gravity feed and by raising or lowering the float level of each bowl!

Run under load via a belt-drive linking the flywheel and load system, it ensures a real world situation and ensuring minimal variation between tests, oil temperature, intake air density and air temperature are all monitored and controlled.

The engine is somewhat agricultural, however its unique ability to vary the compression ratio while running between 5.0:1 and 15.0:1 is quite amazing. The operator simply winds a handle and the entire head and cylinder assembly moves up and down relative to the crankshaft.

A knock sensor measures both the frequency and intensity of the ping (as displayed on a knock metre). Figures are then cross-referenced on a chart using the information provided by the knock meter, plus the height of the head and barrel.

Finally, knock intensity is figured in and the fuel’s octane rating determined.

Taking two hours to warm, this $200,000 engine is super robust and rarely needs rebuilding. Individual tests can then proceed at approximately $120 per test sample.

Being subjected to so much detonation, you can only imagine how much maintenance an engine of this nature must need. Interestingly, this isn’t the case as the piston and rod assembly are rejects from a monstrous ship engine (just kidding)! They’re frigging huge with the incredibly thick piston crown contributing to a combined gudgeon pin and piston weight of 1794 grams! Likewise, the rod weighs an astonishing 1929 grams. The bottom line is these engines which have replacement value of over $200,000 and almost never require rebuilding.


Ultimately, the role of an octane booster, is to regain horsepower lost through detonation or retarded ignition timing due to detonation. But two of our products, the nitro additives, weren’t specifically designed to increase octane. Instead, they contain a mix of nitromethane (the petrol Top Fuellers run) in a "percentage" concentrate. Power Fuel’s Super Street and Max Race additives has 20-percent and 35-percent nitro respectively, and the Australian importer specifically claimed they would increase power, not necessarily octane.

So, we took those two products, and the two best-performing octane boosters to MRT Performance for some Dyno Dynamics dyno testing. Interestingly, we were going to use MRT’s rally Civic, which normally runs on avgas. On PULP – even with the booster – it was pinging too much, so a Jap-spec EF Honda Civic was used with a 1.6-litre VTEC and about 10.0:1 comp ratio.

The graphs tell the story though, and to be fair to the products, with variables such as heat soak, the results weren’t as conclusive as could be gained from an engine dyno. But that is not to say the products don’t work. As our test prove, they do, but it’s not as easily measured on a chassis dyno. Plus the Civic had no detonation problems on PULP, further hampering the "apparent" effectiveness of the boosters.

With changes too small to accurately measure, we would suggest if your engine is sensitive to octane, a booster is for you. If not, try the nitro or racing fuels.


Both the Nulon Pro Strength and the NF Racing Formula rated the best octane boosters in our test. And considering that less NF was needed than Nulon, it evens out a little with a slightly higher cost. Still, both proved extremely effective at increasing octane, even outranking Toluene, which needs much higher levels of concentration. The VP Motorsport 103 fuel was an interesting exercise, and if a little more effort (ie: buying it from the selected outlets) is worth the octane, it’s a good representative of what to expect from straight racing fuel. As for the nitro additives, if you’re not experiencing any type of detonation, they’re definitely worth a try. So whether you detonate or not, we’ve found a fuel additive for you!

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Old 05-06-2010, 10:19 AM   #4
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Re: The Mystery of 'Octane' Finally Uncovered

Mixtures with 92 Octane Premium
10%...94.2 Octane
20%...96.4 Octane
30%...98.6 Octane
Notes: Common ingredient in Octane Boosters in a can. 12-16 ounces will only raise octane 2-3 *points*, I.e. from 92 to 92.3. Often costs $3-5 for 12-16 ounces, when it can be purchased for less than $3/gal at chemical supply houses or paint stores.

Xylene is another alternative...coming when i find that article
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Old 05-06-2010, 10:23 AM   #5
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Re: The Mystery of 'Octane' Finally Uncovered


is another good link
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Old 05-06-2010, 10:26 AM   #6
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Re: The Mystery of 'Octane' Finally Uncovered

and last one for those that crave an octane high...


Enjoy your studying

MSDS on CD-2


and the Lucas product review:


Last edited by 2011CS; 05-06-2010 at 10:34 AM.
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Old 05-06-2010, 10:45 AM   #7
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Re: The Mystery of 'Octane' Finally Uncovered

On the Lucas website you can see on the MSDS that the product contains MMT

Methylcyclopentadienyl solvent

Search that and you find this:


In there you find sold in Canada.. "Cestoburn" by Cestoil Chemical Inc. in Canada.

and their website:




Last edited by 2011CS; 05-06-2010 at 10:47 AM.
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Old 08-28-2010, 02:52 AM   #8
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Re: The Mystery of 'Octane' Finally Uncovered

Is this true or not? Adding mott balls to my fuel tank increases the octane level? Sounds like a weird Idea but my friend tried it to his moped, he said it worked, he dissolved at least 5 balls to a liter of gas
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Old 08-30-2010, 02:59 PM   #9
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Re: The Mystery of 'Octane' Finally Uncovered

Originally Posted by curtisjackson View Post
Is this true or not? Adding mott balls to my fuel tank increases the octane level? Sounds like a weird Idea but my friend tried it to his moped, he said it worked, he dissolved at least 5 balls to a liter of gas
No but if you pour monster energy drink ( the wild berry flavor works best ) you will see a 22hp increase on N/A application V8's
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