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Topic Review (Newest First)
11-07-2004 05:49 PM
Max Keith
mixing fuels

Well I am no chemist or any of that stuff to brag about, but I do have a lot of experience with gasoline and running different octanes in engines. Running a gasoline with a severely higher octane than the engine requires will adversely affect the engines performance as it wont burn effectively, without doing major tuning to use that octane. Ill stack my experience over lab theories any day. The only advantage to running any fuel that is extremely higher in octane than the engine requires is that the engine may run nominally cooler, simply because the combustion isnt complete.

There are also other considerations like specific gravity of fuels, and btu out put to tend with. For instance, AV Gas generally weighs 1/2 lb to the gallon less than does standard pump gas of the same octane, requiring larger jetting.
11-07-2004 01:55 PM
Not necessarily...

Hi folks,
The toluene idea is very viable for use as an octane booster. Modern gasolines have a large percentage of aromatics similar to toluene, around 15-30%. This is where they get alot of their octane rating. I think pure toluene has an octane rating of around ~116 or so? Maybe someone could correct me. If you run a 30% mix of 93 octane/toluene you will get 100 octane, and that would allow significantly increased compression. It is also cheaper if you buy it in larger quantities, and can be obtained for around $2.50/gallon, same cost as gas.

If you run that though you may need to re-calibrate your carb as it can change the specific gravity of the fuel.

Cars will never run worse with high octane than low octane. Running different fuel brings up issues as noted above. However, leaded gas will mess up your O2 sensor permanently if your car is fuel injected. And high octane does not say anything about burn rate, just resistance to detonation. It is due to the molecular structure of petroleum components, ie low octane has an abundance of straight chain hydrocarbons vs. high octane with alot of branched/ring hydrocarbons.

About compression vs. octane, it is a complex issue, primarily relating to compression chamber design. If you have an efficient chamber, especially one like the ford yates head, and run a small chamber with large quench areas and a reverse dome piston, you could probably run 11.5:1 on 93 octane. But, if you take an open chamber head and a domed piston, you would hit 10:1 and be pinging like hell due to total lack of quench area and poor flame travel.

This is certainly an interesting topic!

BTW I am Biochemistry/Organic chemistry major at UW-Madison, so if you have any other chemistry questions feel free and ask! I have to put my useless knowledge to work somehow....
11-06-2004 11:15 PM
lluciano77 At 10.2:1 you should be able to run on 91 octane with no problems.

I have an iron headed 11:1 SBC. It runs on 91.

You are wasting your money on race gas. Your car would run faster with 91 octane. Running too much octane is bad for your engine, and bad for performance.
11-05-2004 08:30 PM
Max Keith
mixing fuels

hmmmmmm Ive never noticed any one particular brand to be any better than any other, with the exception of back in the 70's I used to run Shell gas almost exclusively, because I found its performance to be so much better. ( Couldnt get Sonoco in California). Today, the gas mixtures are combined by govt regulations for specific parts of the US. My Brother In Law owns a Connico bulk plant and he actually tanks gasoline to just about every brand label you can think of in the area, including the Amico and Chevron stations in the area. So in a word, at least in this area, it all comes from the same well.
11-05-2004 05:57 PM
spinn yes, amaco gas is superior

does anyone know why?
11-05-2004 09:13 AM
johnsongrass1 We use a 50/50 mix with VP clear or C12 and Amoco's highest petrol. Never had a problem. Jetting is slightly different than what most carb shop recommend but aren't they all? We are very careful about mixing it so we can be sure of it's repeatablility. VP at 7.67 a gallon we do our best to conserve fuel cost's.
11-05-2004 09:03 AM
RetroJoe Toluene does make a great booster, but as mentioned be very carefull with it. It has a high flash point. Static can set it off. You could probably get away with adding a quart per tank as a booster. I work in a printing plant that uses toluene and safety is the big concern around here! With several 10,000 gallon tanks around, it could make a big boom!
11-04-2004 09:09 PM
Max Keith
fuel mixing

If you arent having any problems with your engine running on hi test pump gas, I wouldnt mess with mixing them. If you are just wanting to get rid of the racing fuel, it probably wouldnt hurt to dump in a gallon or two with each fill up. Running the higher octane fuel, if your engine isnt needing it, can and will hurt your performance. You dont want to run any more octane than your engine actually needs.

The best alternative is to just hang on to it to when its 4 days til payday and you have an empty gas tank.

As for lead substitutes, unless you have a problem with exhaust valve erosion, I wouldnt bother with the stuff. I have run pre unleaded gas engines for several years on unleaded gas and didnt have any problems of that nature. And if you do have a problem with exhaust valve seat erosion, the best thing to do is to take the heads and have hardened valve seat inserts installed.

A word of advice, if you mess with toluene, do it in a well ventilated place, and wear protection on your hands and a real filter mask. Highly toxic stuff.
I used to run a 50/50 mix of 105 AV gas with 91 octane pump gas in a modified I raced. Decided to run it on just the 91 octane once to see what happened. Actually ran better. I was running a 10.5:1 compression ratio in a Cleveland.
11-04-2004 07:22 PM
spinn go to the hardware store, buy a gallon of pure tolulene, mix it with your high test 89. i will find a conversion chart for octane booster,and post a link. i have done this repeatedly on a high comp 318 ,and it stopped the ping . i opened it up years after rebuild and its got clean combustion chambers too.

i think its $3.89 a gal at do it best

man i cant believe im actually recommeding this! so im not,iam just throwing a new idea out there for those who think outside the box. alos i think its the same ting as some offshelf octane boosters. i swear!

Save money...if anyone has actually used this and had a bad expirience they probably mixed wrong.

no tolulene leaves no residue,burns relatively clean shouldNT affect emissions,terribly cancerous

(i dont use in my hotrod)
11-04-2004 07:06 PM
gto67ron No pinging problems. I currently have 1/2 tank of pure Torco Blue 110 I feel that this is a waste of $ and the slow burn could cause me some future problems. I have heard of some peoples engines running worse over time using only the 110 race gas (street driving).
11-04-2004 05:50 PM
Siggy_Freud Just out of curiousity are you having pinging problems or something? I've always read to use as low of octane as you can as higher octanes take longer to burn.
11-04-2004 05:40 PM
Mixing race gas with premium unleaded

I am looking for other opions on the subject of mixing leaded race gas (Torco Blue 110) and premium unleaded 93 octane. I am currently running a 66 GTO with a 400 at approximately 71 to 72 cc chamber volume. My heads are #62 castings that are highly ported with stainless steel valves and NO hardened seats. My compression ratio calculates to 10.2 : 1 I have read about other guys using only the Torco blue with mixed results. If I mix both types of fuels, what is a good ratio and should I use the "lead substitute" to offset the unleaded fuel? Thanks for your comments.

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