lostpilot28

lostpilot28

Well Known Member
OK, don't beat me up too bad for asking this...

I just found out that one of the last remaining local gas stations carrying ethanol free 91 Octane gas will no longer carry it. They can get the 87 Octane grade, though.

I see that my local options are getting scarce...my current solution sends me 20 miles out of the way of my airport to get what I need.

So, my question is whether I can use 87 Octane and an "Octane Booster" without harming my engine or fuel system. I've read where some guys are using 87 Octane and it runs just fine. I don't know if I could do that, although I do have 8.5:1 compression ratio so I can't see why not. But, obviously 91 Octane is preferred.

Does anyone have a solid understanding of whether it is or isn't OK to use Octane Boost additives?
 
hahahaha... This should start WW4000, So I wont say what you should do, or try to defend my answer. All the information and misinformation is out there. I also dont know anything about using additives to boost octane, except to say that some of them will cause your CHTs and EGTs to be hotter. How much Hotter? I have no idea. All I will say on the topic, is if it were my airplane, I would run 87 octane with ethanol that you can get from the cheapest/closest station to the airport. Buy cheap gas. Fly. Have more fun.

Edit: What I fly with now is Ethanol laced 87... No issues whatsoever.
 
To be clear, I'm NOT asking about whether it's OK to use auto gas with ethanol. This question is strictly for non-ethanol auto gas of the 87 Octane variety.
 
Turbo has the right idea, Sonny.

Since 91 Pure has gone away, I've been mixing 1 gallon 100LL to 2 - 3 gallons of 87 Pure. The engines (RV-7 and C172), both 8.5:1, show no differences on the engine monitors from straight 100LL.

I've been thinking of researching - asking - knowledgeable sources, probably oil companies themselves, about much lead, in some easily measurable form, like gallons of 100LL to some amount of unleaded gas, is necessary to boost the octane to mid-90's. But I'm lazy, and relying on something my father-in-law (who ran a Shell refinery in the '70's when lead was being removed from mogas) once told me: A tiny amount of lead added to an 87 octane will significantly boost the octane rating, but the effect diminishes by some root power.

Can anybody beat this anecdotal info with fact?

John Siebold
 
Your father-in-law is correct, but I don't have the numbers either. The first small amount of TEL really brings the octane up; the effect gets smaller as you add more and more.
80/87 (80 Motor octane) avgas has 1 unit (I think it's mg/L or something) of tetraethyl lead; 100LL has 4 units. Maybe some research will turn up how much old 95 and/or 115 octane avgas had.

I do not know if lead plus alcohol is strictly additive, or if they interfere with each other in some way, etc.
 
Pittsbuilder said:
hahahaha... This should start WW4000, So I wont say what you should do, or try to defend my answer. All the information and misinformation is out there. I also dont know anything about using additives to boost octane, except to say that some of them will cause your CHTs and EGTs to be hotter. How much Hotter? I have no idea. All I will say on the topic, is if it were my airplane, I would run 87 octane with ethanol that you can get from the cheapest/closest station to the airport. Buy cheap gas. Fly. Have more fun.

Edit: What I fly with now is Ethanol laced 87... No issues whatsoever.
Click to expand...

Careful..What you say may end up being true but remember some of us run electronic ignitions which can wind the timing out to 40 degrees BTDC at low MP..This is very different from a pair of mags.. Compression ratio is different between engines as well.

We need to know what the "test conditions are" so to speak.

I cureently run 91 ocane in an IO360 with ethanol (electric fuel pumps only) with Pmags and 8.5:1 CR...I want to run 87 octane (cus I'm cheap)and am very interested in others experiences

Frank
 
Interested too!

I am interested too.

Currently running 91 Octane E10 without any problems.
IO-540 8.5:1 CR 1 mag 1 LSE , electric boost pump and mechanical fuel pump.
Mechanical fuel pump has constant flow return line. Provides a trickle of cool fuel to keep the pump from cooking the fuel. Been testing my set up in heat soaked condition using mogas for take off and all seems to run smooth.

I keep avgas in one tank and mogas in the other. Been thinking about switching to 87 Octane especially if I only use it for cruise.
I do believe that the margins for detonation will be further reduced by using an even lower grade of fuel. Remember, Octane is a measure of gasoline's resistance to detonation. However, in a cruise condition of less <65%>power there is little concern for detonation.
I would like to hear from people using 87 Octane mogas E10.
 
You can purchase tetraethyl lead additive from Kemco Industries in Utah. I carry a quart of the stuff with me whenever I'm flying in remote areas where I might want to use 87 octane auto fuel but need to boost the octane. I normally run 91 octane, but sometimes it is not available.

Greg
 
A few of the guys in our chapter use the 1 gal of 100 LL to 5 gal 87 octane mogas strategy. There's nothing wrong with it.

Coming from a motorsports background I've been suggesting this product: http://torcoracefuel.net/pro-accelerator.html.

Unlike the "octane boosters" you find on the shelf at your local O'reilly Napazone, this stuff actually does increase the detonation resistance of the fuel. I first ran into this stuff on the rally circuit. Guys were using pump gas to make race fuel with it to put into their very expensive, very high compression ratio rally cars.
 
$20/qt

My experience is that many of the octaine boosters as so expensive that you're better off adding some 100LL as suggested. I think you'll acheive the same result for a lot less $$. The EtOH is another story...
 
Be Very Careful!!!!!!!!!!

...Many or most of the octane boosters contain chemicals like toluene, tulitane, ethane, naphtha, acetone, Xylene, Methyl-tertiary-butyl-ether, Methanol or Isopropyl alcohol as well as a vast array of other compounds. Aside from most of these dangerously lowering the vapor pressure, being very expensive to use and having very little effect on octane (2 to 3 points at best). The part you really need to be most concerned with is there ability to soften, remove or destroy your tank sealant, as I have had this problem in the past. If you decide you want to do this, here is the formula for what we found on the Dyno to work as well or better than all commercially available products we tested and at a fraction of the cost. Best all, Allan....:D
...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.
.....Disclaimer: this intellectual property is offered to users at no charge. Use it at your own risk. The Anti-Splat-Aero LLC is is not responsible for any damage or problems associated with use of this information. This information is for use by owners on their own personal vehicles and may not be used for profit or sale.
 
Thanks Allan,

You actually measured an incraese in octance using this mixture?..How did you actually measure detonation resistance?

Where does one buy toulene?

Frank
 
frankh said:
Thanks Allan,

You actually measured an incraese in octance using this mixture?..How did you actually measure detonation resistance?

Where does one buy toulene?

Frank
Click to expand...

...In the dyno cell we have knock sensors integrated with our information gathering system that record detonation and its intensity. When the engines are under load it is relatively simple to alter timing in very small steps to check the engines detonation threshold. I used Francisco fuels to purchase most of this type of product in the past. I think they are now out of business here in California due to EPA and whatnot. I am sure a search will produce some sources. Allan....:D
 
Allan,
Thanks a bunch for that information! That is more than I expected. I think it would also be helpful to know how much to add to your gas tank. Would it be one 12 oz. bottle per tank of 87 Octane auto fuel?

Just to be clear, this formula works well with the parts in our RV fuel systems, correct? Toulene, for example, won't eat my mechanical fuel pump seals like ethanol will?

edit: One quick follow up...I'm also interested in whether you have a quantified increase in octane rating. I'm very curious as to what my "new" octane rating would be after adding 12 oz (for example) to a wing-full of 87 Octane.
 
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Diesel is very counter productive to octane rating as is oil. You want the octane increase, stick with straight toluene which is a major component is most race gasolines. 20-25% 100LL is a lot easier, safer, cheaper and convenient though. Plenty of solvent action in toluene as well.
 
Other than what I have read above regarding the effect of the first small amounts of lead, the effect of other octane boosters is simply based on the ratio of the added fuel or other additive.

I notice on the advertisements on the sides of the miracle octane boosters that they do not say how much that small bottle of stuff will increase the octane of a tank of gas. I think Not Much!

Check out the octane calculators available online to make sure your mixture will provide the octane rating needed for your engine.

I studied this stuff for awhile and came to the same conclusions as Ross. That is the best octane booster available to us is 100LL.

Toluene is 114 octane but availability, cost, and potential harm to components easily rule it out in favor of 100LL.

The idea of purchasing lead as a sepaarate additive is interesting though...
 
Avgas from years past used to have a lot of toluene in it. You could smell it in the gas, something like lacquer thinner.

Back in the early 1990's when I first bought my Harley and put on a big S&S carburetor, open pipes and an electronic ignition system that advanced the timing quite a bit, it would ping on hot days under hard acceleration. I would stop by a local hardware store and buy a 32-oz can of toluene for a couple bucks and dump it into the gas tank with 3 gallons of unleaded premium, and no more ping! It ran great. Cans of straight toluene seem to have disappeared from all hardware stores around here, and you have to order it in 5 gallon cans from a dedicated paint supply house.
 
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