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
******** 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
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
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
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.