Backyard Chemistry: Snake Oil or Budget Miracle
Mixing your own race fuel

Backyard Chemistry: Snake Oil or Budget Miracle
The rumor mill in the automotive world is always running at full steam. Anytime gearheads get together, we stand around clucking like a group of hens. One of the rumors winding its way through the Internet, race tracks, speed shops and anywhere gearheads congregate is that anyone can make their own race gas. In an effort to get to the bottom of this, I contacted Dean Hill of New Mexico State University (retired) and Tim Wusz of 76 Performance Products.

A quick search on Google results in a large number of sites promoting the use of race fuel that you blend yourself in your backyard. Any of the racing fuel manufacturers will tell you that this is a fine idea, if you know what you are doing. Many race teams, weekend bracket racers, and hot rod owners have been doing this for years. Blending fuel on your own is totally acceptable if you have all of the necessary information. The racing fuel manufacturers have been providing formulas to the automotive community for decades that dictate how to mix race fuel and street fuel to obtain specific octane and burn characteristics. When you use a formula you find on the Internet to blend your own fuel, you are asking for trouble.

One of the earliest backyard additives was mothballs. In the days of big blocks and carburetors, a common solution to detonation was to add a few mothballs to your fuel. What seemed like a cheap and easy fix could quickly turn into a nightmare. There were three problems facing the potential mothball user. First of all, there have been three different chemicals used in the production of mothballs: napthalene, paradichlorobenzene, and camphor. If you used anything but napthalene-based mothballs, you were only going to make your situation much worse. Secondly, there was no formula for the mix. If you did not add enough mothballs, the engine would still detonate. If you added too many, pre-ignition would occur and tear the motor to pieces. The third problem is a purely modern one. It is difficult to find mothballs in this day and age due to their toxicity. The mothball has gone the way of the dinosaur and is now commonly supplanted by cedar chips or oil for household use.

The latest craze in backyard chemistry goes back a few years as well. The first groups to advocate its use that I can remember are the Buick Grand National and T-Type owners. Since that time, its use has spread throughout the ranks of the import and domestic sub-compacts, late model Ford and GM, and even the carbureted GM, Ford, and Mopar crowd. This backyard chemistry involves mixing toluene, xylene, methyl-tertiary-butyl-ether (MTBE), methanol, ethanol, isopropyl alcohol, or tertiary-butyl-alcohol with transmission fluid and mineral spirits. All of these chemicals can be purchased at your neighborhood hardware store for less than the cost of a gallon of 110-octane race fuel. If you are willing to make a few trips and do a little mixing, you can cut the cost of your fuel bill by at least half. As with most things in life, if it seems too good to be true, it probably is.

There are a couple of major flaws in this bit of chemistry. The first major flaw is the assumption that bulk additives like xylene and toluene create a linear increase in octane. At best, these bulk additives increase octane by a few points and should not be used in amounts greater than 5% - 20%, depending on the additive. Some additives will do no harm above their specified limit. Some become increasingly dangerous. Below is a breakdown of the bulk additives and their limits.



Toluene and Xylene: Both may be used as an additive to increase octane. You may add
up to 20% of either and either will add approximately two
points to the octane number. In general, you are not going to hurt
your engine by adding xylene or toluene. If you add more than
20%, you may as well be dumping it down the drain because you
will find no benefits above 20%. When adding toluene to a base
fuel (such as 92-octane pump gas) the exhaust emissions increase.
Many people could care less about anything other than mandatory
emissions compliance, but your car is trying to tell you that you are
burning fuel less efficiently and losing potential horsepower.

MTBE: MTBE may be used as an additive in quantities of 5% or less.
There are no benefits to be found above 5%. If you are going to
mix your own fuel you are better off spending your hard earned
cash on toluene or xylene.

Methanol: Methanol does not mix well with gasoline. Do not use it.


Ethanol: Ethanol is an interesting case. It mixes well with gasoline,
but has some inherent limitations. The limitation of ethanol
is that unless it has been redistilled with benzene it always
contains 5% water. When used in quantities greater than 10%
it introduces enough water into the system to cause detonation.

Isopropyl Alcohol: Do not use

Here is one of the common Internet recipes for an “Octane Booster”. This is supposed to make eight sixteen-ounce bottles.

100 oz of toluene for octane boost
25 oz of mineral spirits (cleaning agent)
3 oz of transmission fluid (lubricating agent)

We know that toluene will raise octane. However the addition of mineral spirits and transmission fluid do no good whatsoever. The octane increase that would be experienced with the toluene is nullified or severely limited by the inclusion of mineral spirits and transmission fluid. In addition to reducing the overall octane, the inclusion of automatic transmission fluid will reduce horsepower, increase exhaust emissions, reduce spark plug life, increase combustion chamber deposits, reduce the effectiveness of the catalytic converter, reduce the life of the oxygen sensor, and increase crankcase dilution. What this recipe manages to create is a decent cleanser for your garage floor with a nifty red color -- not something to put in a gas tank..

The single most effective additive you can use is tetraethyl lead. All race fuels with ratings greater than 110-octane contain this additive. But even this miracle compound has its share of problems. The first major issue is the simple fact that you (the consumer) cannot buy it. It is an incredibly toxic compound and therefore highly regulated. The second hurdle is that it contains lead. If your car is designed to run unleaded gasoline, you are going to run into a lot of problems trying to run a leaded fuel. You can plan on replacing your catalytic converters and O2 sensors shortly after your experiment with tetraethyl lead.

Dean Hill (who knows how to design fuel; he invented H&H Super Blue, the fuel that powered Bob Glidden to 81 straight wins) recommends Iso Octane (2, 2, 4 Trimethylpentane—a derivative of butane similar to MTBE but lacking methanol) blended with 20% toluene. This will yield a 110-octane race fuel that will knock your socks off. Be prepared to spend some of that cash you are trying to save because Iso Octane is only sold in bulk barrels and it runs about $10/gallon. That is not a real budget miracle, is it? But if you are determined to mix your own fuel, do it right.

Before you run off and try any of this, stop and think for a minute. This is a very basic article and even it should show that it takes more than a little backyard chemistry to produce an effective, safe racing fuel. Nearly all of the chemicals listed are incredibly toxic so please be careful if you are going to try any of this on your own. The best advice I can provide is to leave fuel development to the professionals. I doubt any of you blend your own oil or make your own tires so do not try blending your own fuel. You are more likely to give yourself a new batch of problems than to solve your existing ones.

Denzil Burriss
Denzil@autotechforums.com
11/04/2003

Copyright © by AutoTech Technical Forums and Articles All Right Reserved.

FORMULA 3
Methyl-tertiary-butyl-ether (MTBE)
R+M/2...118
Cost...$3.50/gal
Mixtures with 92 Octane Premium
10%...94.6 Octane
20%...97.2 Octane
30%...99.8 Octane

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.