Octane Booster

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May 28, 2003
Here is an article on "Rocket fuel" for our cars.

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.

Rocket fuel FAQ
Copyright ã 1999,2000 by Eliot Lim This paper may be freely distributed, provided it is distributed in its entirety
Last revised by Eliot Lim: February 8, 2000
Last augmented by Charles Smith: January 6, 2003


In late 1997 I became the lucky owner of 1 out of 150 1998 Porsche 993 Targas, the very last of the air cooled classics. As I drove it through the winter of 1997 and into the spring of 1998 I noticed that the engine lost some of its sweetness. Since this behavior was strongly related to ambient and engine temperature I suspected that the engine electronics were retarding its ignition timing due to insufficient fuel octane.

I started experimenting with octane boosting by first adding small doses of over the counter octane boosters and noticed immediate improvement. The engine ran smoother and quieter, was more willing to rev and had noticeably sharper throttle response. The octane shortage was confirmed by the sticker on the filler cap that stated that 93 octane fuel was needed. Since the highest octane rated fuel that was commonly available in Washington state is 92, I decided to investigate long term cost effective octane boosting so that I could fully enjoy the performance that this car offered.

My other car at the time, a 1990 Audi V8 quattro had an even more dramatic response to octane boosting. I managed to convince a few good friends to try it and the reaction was overwhelmingly positive. When I attempted a broader based dissemination of this exciting find, I was greeted largely by broad unyielding skepticism and plenty of FUD (fear, uncertainty, doubt) regarding toxicity, safety and engine damage. There arose a need to more clearly explain the details of octane boosting, hence giving rise to this article.

Q: Will my car benefit from octane boosting?

A: Consumer organizations have effectively emphasized the larger markups that oil companies charge for high octane gasoline, implying that for most vehicles higher octane fuel is a complete waste of money. It has been quite a long time since the consumer alert was issued. Since then engine technology has evolved greatly, while people's perceptions generally have not.

Modern vehicles now use computerized engine management systems that can react to engine knock and retard ignition timing if low octane fuel is being used. Consequently cars are now being manufactured with very high compression ratios that appear to give good fuel economy and at the same time good performance. This combination does assume that fuel of adequate octane is being used.

Q: Why bother to boost octane at all since my engine can run just fine on lower octane fuel?

A: For a high compression engine to run on low octane fuel, the engine management system will need to retard the ignition timing to prevent preignition or pinging. Retarding the ignition timing means that the firing of the spark plug is delayed until a later moment in the compression stroke. It does not take much to see that a later onset of combustion means that the combustion is less complete, which in turn mean less power and poorer fuel economy. It is possible that the casual driver will still come out ahead in terms of saving money by using low octane fuel, but the retarded ignition advance also means a rougher running engine and a much duller throttle response. Thus octane boosting is not necessarily of interest to all motorists but rather the enthusiasts.

For turbocharged or supercharged engines, insufficient octane will also lead the engine management system to curtail the amount of boost which in turn defeats the purpose of these engines.

Q: How did you discover using toluene?

A: Someone came across a web page that described various DIY home brew octane booster formulas. One of which used toluene as its main ingredient. As a Formula 1 racing fan of many years, I recalled that toluene was used extensively in the turbo era in the 1980s by all the Formula 1 teams. The 1.5 liter turbocharged engines ran as much as 5 bars of boost (73 psi) in qualifying and 4 bars (59 psi) in the actual race. Power output exceeded 1500bhp, which translates into 1000bhp/liter, an astronomical figure.

A motorsports journalist, Ian Bamsey, was able to obtain Honda's cooperation for his book "McLaren Honda Turbo, a Technical Appraisal". The book documents the key role that the toluene fuel played in allowing these tiny engines to run so much turbo boost without detonation. The term "rocket fuel" originated from the Formula 1 fraternity as an affectionate nickname to describe its devastating potency. Thus I concluded that I should focus my research on using toluene for my octane boosting project.

Individuals with good long term memory will recall that when unleaded gasoline was first introduced, only low octane grades were available. While it is not entirely clear that high octane super unleaded gas came about as a result of the advances in fuel technology in Formula 1, there is every reason to suspect that this is indeed the case, since many of the major oil companies were involved in the escalating race to develop increasingly potent racing fuel during this era.

Q: Why do you think toluene is better than other types of octane boosters?

A: Several reasons:

Mindful of the evil reputation of octane boosters in general, toluene is a very safe choice because it is one of the main octane boosters used by oil companies in producing ordinary gasoline of all grades. Thus if toluene is indeed harmful to your engine as feared, your engine would have disintegrated long, long ago since ordinary pump gasoline can contain as much as 50% aromatic hydrocarbons.

Toluene is a pure hydrocarbon (C7H8). i.e. it contains only hydrogen and carbon atoms. It belongs to a particular category of hydrocarbons called aromatic hydrocarbons. Complete combustion of toluene yields CO2 and H2O. This fact ensures that the entire emission control system such as the catalyst and oxygen sensor of your car is unaffected. There are no metallic compounds (lead, magnesium etc), no nitro compounds and no oxygen atoms in toluene. It is made up of exactly the same ingredients as ordinary gasoline. In fact it is one of the main ingredients of gasoline.

Toluene has a RON octane rating of 121 and a MON rating of 107, leading to a (R+M)/2 rating of 114. (R+M)/2 is how ordinary fuels are rated in the US. Note that toluene has a sensitivity rating of 121-107=14. This compares favorably with alcohols which have sensitivities in the 20-30 range. The more sensitive a fuel is the more its performance degrades under load. Toluene's low sensitivity means that it is an excellent fuel for a heavily loaded engine.

Toluene is denser than ordinary gasoline (0.87 g/mL vs. 0.72-0.74) and contains more energy per unit volume. Thus combustion of toluene leads to more energy being liberated and thus more power generated. This is in contrast to oxygenated octane boosters like ethanol or MTBE which contain less energy per unit volume compared to gasoline. The higher heating value of toluene also means that the exhaust gases contain more kinetic energy, which in turn means that there is more energy to drive turbocharger vanes. In practical terms this is experienced as a faster onset of turbo boost.

Chevron's published composition of 100 octane aviation fuel shows that toluene comprises up to 14% alone and is the predominant aromatic hydrocarbon. Unfortunately composition specifications for automotive gasoline is harder to pin down due to constantly changing requirements.

Chevron's web site also describes the problems of ethanol being used in gasoline.

MTBE was heavily touted as a clean additive several years ago, and became a key ingredient in reformulated gasoline that is sold in California. But recently new studies arose that showed that MTBE was far more toxic than previously imagined. Organizations such as oxybusters have formed around the country to eliminate the use of MTBE in gasoline and several states, including California have passed new laws to eventually outlaw MTBE.

Q: How much toluene should I use per tank of gas?

A: Octane ratings can be very easily calculated by simple averaging. For example, the tank of an Audi A4 1.8TQ is 15.6 gallons. Filling it with 14.6 gallons of 92 octane and 1 gallon of toluene (114 octane) will yield a fuel mix of:

(14.6 * 92) + (1 * 114) / 15.6 = 93.4

The Audi A4 1.8T is a good example of a car that has very high octane needs if it has been modified to produce more turbo boost. The base compression ratio of this car is a very high 9.5:1 and when an additional 1 bar (14.7 psi) of turbo boost is applied on top of it, the resulting effective compression ratio is way beyond what 92 or 93 octane fuel can ever hope to cope with. Most modified 1.8Ts running without octane enhancement are running with severely retarded ignition timing and boost.

Q: Will toluene damage my engine or other parts of my car?

A: A 5 or 10% increase in the aromatic content of gas will most likely be well within the refining specifications of gasoline defined by ASTM D4814, which specify an aromatic content of between 20% and 45%. What this means is that if the 92 octane gas that you started off with had an aromatic content of say 30% and you increased it by 10% to 40% you would still be left with a mix that meets the industry definition of gasoline. So the above question would amount to: "Will gasoline damage my engine or other parts of my car?"

Even in the unlikely event that the 92 octane gas has a aromatic content of 45% the resulting mix would still be within the bounds of gasoline sold in other countries.

Q: Isn't toluene an extremely toxic substance?

A: The common perception of toluene's toxicity far exceeds reality. Fortunately there is an ample body of information available that specifically addresses this question. Toluene is more toxic than gasoline but it is certainly not agent orange or cyanide. See the Agency for Toxic Substances link below in the reference section.

US Environmental Protection Agency Chemical Summary

US Agency for Toxic Substances and Disease Registry (ATSDR)

National priority list of toxic substances
Note that the ATSDR also rates gasoline as a hazardous substance.

Mobil's spec sheet for toluene even goes as far as saying that "Based on available toxicological information, it has been determined that this product poses no significant health risk when used and handled properly."

Q: Isn't toluene an active ingredient of TNT (trinitrotoluene) and is thus deadly?

A: In the same way that cotton wool is the base ingredient of nitrocellulose (guncotton) which in turn is the main ingredient in modern smokeless gunpowder. Using this reasoning one could conclude that cotton wool is a deadly substance. This question reflects a poor understanding of basic chemistry but unfortunately it has been asked often enough.

Q: How much does toluene cost, and where can I buy some?

A: $10/gallon in a one gallon can at a hardware store, about $6/gallon in a 5 gallon can from a chemical supply or paint store, or $3/gallon in a 55 gallon drum from a chemical supply warehouse.

A2: Experience of Charlie Smith in 2002. Sherwin Williams paint stores have it for $5.00 in a gallon can. They can order it in a 5 gallon can at $4.00 / gallon. They can order 55 gallon drums for about the same cost per gallon, but you have to have a dock unloading facility to get the drum(s) off of the delivery truck.

Q: Can I just dump in 100% toluene into the tank like the F1 racers? vroom vroom vroom

A: First of all, the F1 racers did not use 100% toluene, but 84%. The other 16% in their brew is n-heptane, which has an octane rating of zero. The reason for this strange combination is because the F1 rocket fuel was limited to the rules to being of 102 RON octane. The n-heptane is "filler" to make the fuel comply with the rules.

Because toluene is such an effective anti knock fuel it also means that it is more difficult to ignite at low temperatures. The Formula 1 cars that ran on 84% toluene needed to have hot radiator air diverted to heat its fuel tank to 70C to assist its vaporization. Thus too strong a concentration of toluene will lead to poor cold start and running characteristics. I recommend that the concentration of toluene used to not exceed what the engine is capable of utilizing. i.e. Experiment with small increases in concentration until you can no longer detect an improvement.

Q: Why not simply use racing gasoline or aviation fuel?

A1: Most types of aviation fuel have very high lead content, which would rule out cars equipped with catalytic converters. Most piston engined aircraft burn leaded fuel. Also aviation fuel has a very different hydrocarbon mix to optimize volatility properties at high altitude.

A2: Racing gasoline could be a much more convenient way to run high octane fuel compared to having to constantly mix in toluene with each fill up. There are, however a few caveats:

You don't know for sure if you are really getting what is being advertised. You should find out if the fuel inspectors verify the actual octane of the racing gasoline in addition to ordinary gasoline. If you paid $3/gallon and only got 94 or 95 octane instead of 100 octane you may conclude erroneously that your car does not benefit from octane boosting.

You don't know what octane boosters are used in the racing gasoline. The worst case scenario is buying leaded racing gasoline without knowing it. Unleaded racing gasoline may still contain damaging octane boosters like MMT or methanol. A very high alcohol content will lead to fuel line erosion, accelerated fuel pump wear, very poor fuel economy and possibly lower performance, as alcohols have a less impressive MON rating than aromatics.

It takes smaller quantities of toluene to achieve the same octane boost compared to 100 octane racing gas. I have not seen unleaded racing gas for sale that exceeds the octane rating of toluene.

Since toluene is not officially sold as a fuel, gas taxes do not apply. Also racing gasoline tend to have higher markups being of interest to the performance minded enthusiast and thus is very likely to be more expensive to buy and use long term than toluene, which is typically used in more mundane applications like paint thinner.

Q: Ok, what is the catch?

A: It should be mentioned that in the US, efforts are underway to reduce the aromatic content of gasolines in general as a higher aromatic content leads to higher benzene emissions. Benzene is an extremely toxic substance. However it should also be noted that the proportions that is being discussed in this FAQ is relatively small and in the grand scheme of things is probably insignificant. Moreover, the industrial standard for defining gasoline composition allows plenty of leeway in aromatic content and the proportions present in US gas is already lower than most other countries. I therefore feel that the information provided here is useful to a performance minded car enthusiast while not being significantly detrimental to the environment.

Q: What safety measures can you recommend in handling toluene?

A: The following is a good reference guide:

Q: Do you have testimonies of others who have tried this?

A: Some samples of feedback is reprinted with the names removed below. You may contact me if you wish to contact the respondents directly.

Since I didn't have any reference point for how much to use, I dumped about a half gallon of this mix into a mostly empty tank (the GT has a 16 gallon tank) and then filled up with Chevron 92 octane.
I didn't get to drive the car until PIR the next morning, (my GF doesn't like the 200; it's too big) but the report was that there was no change for a mile or so, and then all of a sudden, the engine seemed to smooth out and became quite eager to rev and run.
Well, by that calculation, I only managed to bump the octane to just shy of 93, but it seemed to make a big difference. I ran the car hard all day, (for reference, it's got an '87 MC turbo motor, K26, 12psi boost, and currently no intercooler) and even at 12 pounds of boost, I never once felt the ECU backing the timing off. Granted, the ambient temps never got above 50, and my water and oil temps were rock solid. (Oil just pushing above 100C)

The only cars that I had to get out of the way for was an Integra Type R and a couple of race-prepped P-cars. I even managed to lap the NSX once! It was a really good day!

Okay, kids, gather round. This is important: we spend lots of money for our car, lot of money modifying and taking care of it, lots of effort and pride in owning it. So if someone comes along and proposes to give you something that would increase your enjoyment in driving by exponential measures and it would only cost you two or three bucks per tank of gas, would you be suspicious like the 100MPG carburetors? Would you listen long enough to real-life testimonies to consider this improvement for yourself?
Well, this is the case for Toluene and what it can do for your V8Q if you been using anything less than 92+ octane. Get some.Try it. No harm, no risk. Use about 24-32 ounces per 1/2 to full tank. You will not look debonair. You will have to suspend your "cool" look. You may want to try this alone. YOU WILL HAVE THE ****TEST, MOST PLASTER, GRIN ON YOUR FACE YOU HAVE EVER HAD! It won't come off. You'll tell the kids, daddy has his own "transformer". It will be like a new car...no, better than new!
I took my family out to dinner tonight and could hardly keep from dropping it into manual and showing off like some teenager (I don't think my 17 year old daughter was inpressed). I wanna see some posts here with personal experiences by you guys using this stuff - I wanna know that my car is normal and hasn't been deprived ever since I've owned it.

I did the Rocket Fuel thing tonight on my Extremely Modified 5KCSTQ that runs 24 PSI of boost... And I can tell you not only does my ears and my butt say that the Rocket fuel is doing it's job but My ECU Data logger that gives me the timing value for all 5 cyls says it's working too.
Before Rocket Fuel I was running full retard (14 Deg of timing) on boost and would still on occasion get some knock, now I'm getting timing numbers around 22 Deg's with ZERO knock ever. I'm running 2 Gallons of Toluene 7oz of ATF and 17.5 gals of 93 oct gas for a net octane of 95.15. I'm next going to try 3 Gallons of Toluene (96.23 Octane) to see what timing numbers I get.

After being convinced that my car was running below it potential - Owners manual recommends octane rating between 95 and 99, although it_will_run on octane as low as 91 - I stopped by Sherwin Williams and picked up a gallon. It was on sale for $5.85! Anyway, head to the chevron and pour a half gallon into the tank before pumping in the premium. The car took 16 gallons so there was still 4 gallons in the tank. I take off....nothing (obviously burning the fuel still in the lines). About 10 miles later, HOLY SH*****T!!!!!!!!!! It really does everything advertised by the list. It is so much more responsive from a stop and low speed, it really is impressive. I would agree with the sentiment that it feels like a totally different car.
For the non believers, you really should try to get some higher octane fuel in your tank, whether through the use of Toluene or not. The owners manual recommends 95 to 99 octane** for optimal performance. With the half gallon of Toluene I added to the 92 octane, I was only running at approximately 92.6 octane and the difference was simply amazing!

If you haven't tried it, do yourself a favor and give it a whirl - I swear you'll be impressed.

(**note: this person confused RON octane mentioned in the owners manual with R+M/2 octane that is sold in the pump. 95-99 RON is roughly equivalent to 91-94 R+M/2)

After trying rocket fuel for two weeks, I can only say I love it.
The first tank, however, was a disappointment. I think I did not add enough of rocket fuel for the first tank. So I added a little more for my second tank, it ran better but not too much improvement. Then on my 3rd tank, what a difference, the car feels like a "Rocket" now, even though it is an "Auto". I always feel there is more power available for me.

I think for my 1st and 2nd tank, I did not have enough rocket fuel in it, even though I added one gallon per tank. Then, on my 3rd tank, I had enough because of the left overs from my 1st and 2nd tank. (I fill up my tank at about the 1/4 mark). Now I only have about 2 gallons of rocket fuel left, I better get more now!!! :)

Reference materials:

1. Gasoline FAQ

2. McLaren Honda Turbo - a technical appraisal
Ian Bamsey
ISBN 0-85429-840-1, published 1990

3. Chevron's excellent Motor Gasolines Technical Review

4. Agency for Toxic Substances FAQ on Toluene
In summary:
Use in a well ventilated area, don't drink even a little of it, and
report spills of more than 1000 pounds to the National Response Center

5. Toxic Chemicals in your Environment (Australia) FAQ on Toluene
In summary:
this "Total Environment Center" likes a totally chemical free environment,
and even at that they can't find fault about much more than acute exposure
cases, and they also say not to drink any of it.

6. Exxon Chemical Americas - Toluene, Technical Material Safety Data Sheet

7. Recicladora Temarry de Mexico - Recycling Processor
Recycling information and Material Safety Data Sheets on numerous chemicals including Toluene.
Very interesting. Living in CA where we can only get 91 octane at the pump, and owning two cars that require 92 octane fuel, I might give this a try.
FYI, I have seen this before and I posted it on a motorcycle forum. I got some intresting replies. In some states Toulene is a controlled substance. One of the cops on there said it can be used for making drugs (crack). Another guy in Texas was using it by the gallons for his race car and the cops did a raid on his house and shop thinking he was making crack he was not. But got a large $$$$ fine for having to much.
Well.....I must say that I have to see more info and tests before I am a believer. 110 octane race fuel is 4 bucks a gallon around here, and I ran it in a 12.5CR SBC I had, as the CR forced me to do so. I tried it in my camaro once and saw no difference compared to the 93 I usually run. Now my camaro is not a turbo, has no computer and does not run EXTREMELY high compression, but it is around 10, and has a strong advance curve. I would like to hear from someone who has tried the toluene in their vehicles though.
Tolly is great.
Allows more advance.
Allows greater compression ratios.
Allows more power.

Mixes easily with petrol, as well as a lot of the fuel type alocohols.

Is strongly carcinogenic.
Will attack rubber parts in high doses.

I used to use it a lot, to boost the octane of whatever mess I was playing with at the time.

I doubt the statement about F1 teams using a fuel based almost entirely on toluene.

In a road engine, any fuel that has a clear and sharp evaporation point (i.e. alomst pure substance like toluene, benzene, methanol etc etc) will be a hard starter with driveability issues
Most production street cars, even high performance ones, are not going to benefit from anything higher than the recommended octane. So it only really becomes an issue if you are unfortunate enough to live in a state that has made unavailable the 92 (or 93) octane your engine was intended to burn (like California).

Running 91 in an engine designed for 92, may or may not make a noticeable difference. But if you really want that 92 octane your car was intended to run, you only need a 1:20 ratio from Toluene to 91 octane gasoline. Now if that 1 gallon of Toluene costs $10 and you have a 20 gallon tank, you just added almost $10 to the cost of a fillup.

Considering that some stations sell 100 octane unleaded race fuel and out here it usually costs around $4 to $4.5 per gallon, the toluene approach sounds like the bargain alternative.

I could see doing something like this for autox, road racing or 1/4 mile runs. But for everyday driving, it seems like overkill.
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