Reader Question

A reader asks:

I am fortunate to have acquired a Honda RC 51. I live in a very small town in Oklahoma about fifteen miles from Kansas. The owners manual says to use 92 octane unleaded. The gas stations here dont sell it. I have thought about using some octane booster, but that stuff is a ripoff at 6.50 for 16 ounces. The main ingrediant in it is Toulene, to boost the octane. Should I use this or should I run on a lower octane and forget about it. Will running on a lower octane mess up any of the systems. Will altering the gasoline with toulene to acheive a higer octane be detrimental to the system. I really don't want to mess with the bike, I plan on having it for a long time. Your help would be much appreciated.

MO writes:

You probably have 91 octane, which should be fine, the bike willcompensate, and it's probably even safe on 88 octane.

You don't have Sunuco 94 octane there? Or Amaco 93? They're premium fuels, we used them in our AMA Profession racing team -- the hot setup was to mix Amoco 93 half-and-half with our 110 octane leaded race fuel, then you get all the octane (mixing didn't seem to lower the octane and we ran gobs of compression) and you get all the exciters and oxygenators that're in pump gas these days.

Here is a collection of information the reader also sent in:

Note in the story, if my memory serves me correctly, MTBE is a carcinogen, and a pretty nasty chemical all-around. Not that toulene and the others aren't.

The easiest way to get octane is to mix toulene in your fuel. Or mixleaded race gas with pump gas.

Octane BoostersI pulled this off the Vette list last year. It's not as complete as Ithought, but there's some good info here. First part is Sunoco Fuel info, the second is about various octane boosters and how to mix your own brew.

First, some data about the Sunoco CAM2 fuels from their literature:SUNCO Fuel Color Research Octane Motor Octane (R+M)/2 Specific Gravity ReidVapor Pressure Distallation Temp, deg FInitial 10% 50% FinalStandard Purple 115 107 111 0.725 8# 90 160 220 360GT Unleaded natural 105 95 100 0.760 8# 90 150 210 230Supreme Blue 116 109 112 0.715 8# 90 155 215 260Maximal Red 118 115 117 0.700 6# 100 150 220 240And from Rich Lassitter's article in the GS Xtra ... how to mix your ownbrew:Formula (R+M)/2 Cost Mixtures with 92 Octane Premimum Note10% 20% 30%Toulene 114 $2.50/gal 94.2 Octane 96.4 Octane 98.6 Octane (1)Xylene 117 $2.75/gal 94.5 Octane 97.0 Octane 99.5 Octane (2)Methyl-tertiary-butyl-ether (MTBE) 118 $3.50/gal 94.6 Octane 97.2 Octane99.8 Octane (3)Methanol or Ethanol 101 $0.60 - $1.75/gal 94.3/94.7 Octane Not RecommendedNot Recommended (4)Isopropyl Alcohol and Tertiary Butyl Alcohol 101 $0.60 - $1.50/gal 94.5Octane Not Recommended Not Recommended (5)


1. Toulene: 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 for12-16 ounces, when it can be purchased for less than $3/gal at chemical supply houses or paint stores.

2. Xylene: Similar to Toulene. 12-16 ounces will only raise octane 2-3*points*, i.e. from 92 to 92.3. Usually mixed with Toulene and advertised as *race formula*.

3. Methyl-tertiary-butyl-ether (MTBE): Oxygenate. Very common in octane booster products. Has lower BTU content than toulene or xylene, but oxygenate effect makes the gasoline burn better and produce more energy.

4. Methanol or Ethanol: Methanol is wood alcohol. Ethanol is grain alcohol and found in Gasohol in 10% ratios. Both alcohols are mildly corrosive and will eat gas tank linings, rubber and aluminum if used in excessive ratios. Main ingredient in "Gas Dryers", combine with water.

5. Isopropyl Alcohol and Tertiary Butyl Alcohol: Similar toMethanol/Ethanol. Isopropyl Alcohol is simply rubbing alcohol.

Making your own

How to make your own octane booster (this is the basic formula of one of the popular octane booster products). To make eight 16 ounce bottles (128 oz = 1 gal):

100 oz of toulene for octane boost

25 oz of mineral spirits (cleaning agent)

3 oz of transmission fluid (lubricating agent)

This product is advertised as "octane booster with cleaning agent *and* lubricating agent!". Diesel fuel or kerosene can be substituted for mineral spirits and light turbine oil can be substituted for transmission fluid.

Color can be added with petroleum dyes.

-- Ken Mosher

-- Buick Grand National: A *BOOST* of Buick Performance

[Thanks a bazillion for that post. I'll only add one comment regarding using methanol. In a word, don't. It attacks zinc and magnesium very rapidly. Guess what is in carburators and other fuel system parts. I had this graphicly demonstrated to me one time. I was involved in racing chain saws (Oh no, not another one....) In the particular class, my saw ran on 100% methanol. Saws are typically made of a magnesium alloy. I knew I had to clear out the system after each run but one afternoon I forgot. By late evening when I remembered it, the gas tank had already corroded through. I left it to see what would happen and by morning practically the entire saw was a pile of white dust with steel parts interspersed. That included my one-of-a-kind highly ported cylinder I'd spent hours on. *sob*. I saw similar results running methanol in motorcycle engines, though never as bad. JGD]

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