Tetra-ethyl lead

brien23

brien23

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Brien
Is Tetra-ethyl lead going away in 100LL and replaced with 94UL. It's beeen on the back burner for a long time but now seems to be out front again.
 
brien23 said:
Is Tetra-ethyl lead going away in 100LL and replaced with 94UL.
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Not in this country. Since 70% of the avgas in the USA is burned by airplanes with engines requiring 100 octane fuel, I'm pretty sure 100LL wpn't go away until an unleaded fuel that will work in all our engines becomes available, and there are two such fuels currently in testing. When that day comes, I'll be very happy to see it as that will end the need for me to pick lead out of spark plugs once and for all, and nobody will be motivated to carry TCP around in the plane with them and risk this happening.
 
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Ron Levy said:
Not in this country. Since 70% of the avgas in the USA is burned by airplanes with engines requiring 100 octane fuel, I'm pretty sure 100LL see go away until an unleaded fuel that will work in all our engines becomes available, and there are two such fuels currently in testing. When that day comes, I'll be very happy to see it as that will end the need for me to pick lead out of spark plugs once and for all.
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Are you sure all those engines need all the lead contained in 100LL?
 
dmccormack said:
Are you sure all those engines need all the lead contained in 100LL?
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No, and I didn't say they needed lead in any quantity, just that they need 100 octane fuel. As NASCAR/Sunoco and a couple of avgas researchers have shown, it's possible to make a 100 octane fuel without TEL, and that should take care of those engines requiring 100 octane fuel.
 
Ron Levy said:
No, and I didn't say they needed lead in any quantity, just that they need 100 octane fuel. As NASCAR/Sunoco and a couple of avgas researchers have shown, it's possible to make a 100 octane fuel without TEL, and that should take care of those engines requiring 100 octane fuel.
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What percentage of GA engines actually need 100 octane, vis 87?
 
dmccormack said:
What percentage of GA engines actually need 100 octane, vis 87?
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You would probably want to take into account the annual utilization of both engine types. A C-421 flying 300+ hr/yr on charter duty is going to burn a bunch more fuel than a weekender behind a single O-320.


Trapper John
 
Trapper John said:
You would probably want to take into account the annual utilization of both engine types. A C-421 flying 300+ hr/yr on charter duty is going to burn a bunch more fuel than a weekender behind a single O-320.


Trapper John
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No problem...but what were the advantages of 100ll over the old 87 octane that required all GA airplanes to now use 100ll?
 
dmccormack said:
No problem...but what were the advantages of 100ll over the old 87 octane that required all GA airplanes to now use 100ll?
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higher octane gas has more resistance to auto ignition.
 
dmccormack said:
No problem...but what were the advantages of 100ll over the old 87 octane that required all GA airplanes to now use 100ll?
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oh i think i misunderstood your question.

Demand.

I would occasionally burn through 200 gallons of 100LL on one trip in the 421. That is about a years worth of fun flying in the Chief.
 
TEL is/was used as an octane booster (and to a significantly lesser extent lubricant) which reduces the probability of "engine knocking".
 
dmccormack said:
No problem...but what were the advantages of 100ll over the old 87 octane that required all GA airplanes to now use 100ll?
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Back in the old days we had 80/87 and 100/130 (and 115/145 for the supercharged radials). I think it was largely an economic decision on the part of the oil companies to produce just one fuel, 100LL. There was no advantage for low-compression engines to run 100LL, but that became the only choice before auto gas STCs. 100LL has something like 4x the lead of 80/87, no one had lead fouling problems way back when.


Trapper John
 
tonycondon said:
oh i think i misunderstood your question.

Demand.

I would occasionally burn through 200 gallons of 100LL on one trip in the 421. That is about a years worth of fun flying in the Chief.
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I've burned through 100+ gallons in a Single on a weekend, but in each case the engine was designed and delivered back when 87 octane was the only type available.
 
dmccormack said:
No problem...but what were the advantages of 100ll over the old 87 octane that required all GA airplanes to now use 100ll?
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100LL has no advantage over 80/87 octane avgas for low compression engines. Avgas 80 was eliminated because keeping both in the system wasn't economical and 100LL was deemed sufficient for all aircraft that could run on Avgas 80. FWIW, Avgas 80 also has lead, albeit a lot less than 100LL.

BTW, the folks at GAMI have an unleaded avgas formula that they've been testing for a while that has the potential to replace 100LL in all current applications without engine modifications. According to GAMI's George Braly production cost should be comparable to 100LL.
 
gismo said:
100LL has no advantage over 80/87 octane avgas for low compression engines. Avgas 80 was eliminated because keeping both in the system wasn't economical and 100LL was deemed sufficient for all aircraft that could run on Avgas 80. FWIW, Avgas 80 also has lead, albeit a lot less than 100LL.

BTW, the folks at GAMI have an unleaded avgas formula that they've been testing for a while that has the potential to replace 100LL in all current applications without engine modifications. According to GAMI's George Braly production cost should be comparable to 100LL.
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Right -- 87 octane had less lead, and was used in various engines we still use today (IO-360, 470, 520, 540, 550, etc etc).

So what percentage of GA flying needs 100ll?
 
kevin47881 said:
TEL is/was used as an octane booster (and to a significantly lesser extent lubricant) which reduces the probability of "engine knocking".
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The idea that TEL provides some form of lubrication is an OWT that just won't die. IIRC that rumor came from the Ethyl Corp. whose marketing department made that up to make their product seem more beneficial.
 
dmccormack said:
Right -- 87 octane had less lead, and was used in various engines we still use today (IO-360, 470, 520, 540, 550, etc etc).

So what percentage of GA flying needs 100ll?
Click to expand...

To be more specific, it would be interesting to know what engines need
100LL, and what engines only would need, say, 94 octane fuel.

My own O-320 currently requires 100LL (by STC). I can no longer
use 80/87 or autogas.
 
dmccormack said:
Right -- 87 octane had less lead, and was used in various engines we still use today (IO-360, 470, 520, 540, 550, etc etc).

So what percentage of GA flying needs 100ll?
Click to expand...

Any engine that is turbocharged or has a compression ratio greater than about 7:1 requires more octane than is provided by Avgas 80. That includes most but not all injected (e.g. IO-360, IO-470) and quite a few carbureted large bore engines. I can't say what percentage of the fleet requires more octane than Avgas 80 but I'm certain it's substantial. And as someone already pointed out, the aircraft that need 100LL burn fuel at a much higher rate on the average than the ones that don't. I'll bet I can count the 65 HP four bangers at my airport that burn 50 or more gallons of fuel per month on one hand and still have four fingers and a thumb left over. And that's not because there aren't any, I personally know of at least 10 and I'm sure there's more I don't know of.
 
Trapper John said:
Was that a 160 HP conversion with higher comp pistons?
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yes sir.

I converted my 150hp engine in my cherokee 140 to the mighty
160hp. It was really hard to find 80/87 or non-alcoholic autofuel
around KBED.

Even with the standard cruise prop my 140 climbs better than
before the engine overhaul.
 
gismo said:
Any engine that is turbocharged or has a compression ratio greater than about 7:1 requires more octane than is provided by Avgas 80. That includes most but not all injected (e.g. IO-360, IO-470) and quite a few carbureted large bore engines. I can't say what percentage of the fleet requires more octane than Avgas 80 but I'm certain it's substantial. And as someone already pointed out, the aircraft that need 100LL burn fuel at a much higher rate on the average than the ones that don't. I'll bet I can count the 65 HP four bangers at my airport that burn 50 or more gallons of fuel per month on one hand and still have four fingers and a thumb left over. And that's not because there aren't any, I personally know of at least 10 and I'm sure there's more I don't know of.
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I'm not suggesting the national aviation fuel supply be changed to meet the needs of the few antique airplane fliers -- but it seems there are many problems introduced by 100ll (airplane and environmental) that superficially appear unjustified.

In other words, given that the vast majority of GA airplanes flown regularly were designed for 87 Octane, what problem is 100ll solving?
 
dmccormack said:
I'm not suggesting the national aviation fuel supply be changed to meet the needs of the few antique airplane fliers -- but it seems there are many problems introduced by 100ll (airplane and environmental) that superficially appear unjustified.

In other words, given that the vast majority of GA airplanes flown regularly were designed for 87 Octane, what problem is 100ll solving?
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the refiner doesnt care that 70% of airplanes don't need 100LL. they care that they can't sell enough 80/87 or whatever to make it justifiable. Plus they don't feel bad because they know that that 70% can run on 100LL if they have to, the problems can be dealt with.
 
tonycondon said:
the refiner doesnt care that 70% of airplanes don't need 100LL. they care that they can't sell enough 80/87 or whatever to make it justifiable. Plus they don't feel bad because they know that that 70% can run on 100LL if they have to, the problems can be dealt with.
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Sure, engines designed for 80/87 can run on 100ll, but not without impact:

1) increased lead exhaust (environmental)
2) engine problems due to lead fouling (maintenance)
 
dmccormack said:
Sure, engines designed for 80/87 can run on 100ll, but not without impact:

1) increased lead exhaust (environmental)
2) engine problems due to lead fouling (maintenance)
Click to expand...

if the refiner can't make money selling 80/87 why do they care?
 
dmccormack said:
Sure, engines designed for 80/87 can run on 100ll, but not without impact:

1) increased lead exhaust (environmental)
2) engine problems due to lead fouling (maintenance)
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I think the complaint department closed about 30 years ago...


Trapper John
 
Bob Noel said:
yes sir.

I converted my 150hp engine in my cherokee 140 to the mighty
160hp. It was really hard to find 80/87 or non-alcoholic autofuel
around KBED.

Even with the standard cruise prop my 140 climbs better than
before the engine overhaul.
Click to expand...

That's probably a better way to spend the money than getting an autogas STC - IIRC the Cherokees require an extra electric fuel pump for autogas that runs the price up quite a bit compared to a gravity feed Cessna where the STC is just a couple of stickers.


Trapper John
 
dmccormack said:
What percentage of GA engines actually need 100 octane, vis 87?
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I have no idea. Note that there are also a lot of GA engines (like mine) which were certified for 91/96 and can't run on 80/87 but could run on 94UL. All I know is what I read -- that 30% of the piston aircraft in operation require 100 octane, so the other 70% could run on something less than 100 octane (e.g., the 94UL) but not necessarily 80/87. I don't know what percentage of the fleet planes would be unable to operate on 80/87, but I know it would include every 160HP 172, Piper Archer/180 Cherokee, Grumman Tiger, Beech Sundowner, etc, with an engine originally certified for 91/96. I suspect that's quite a few planes.
 
Dan,

You may occasionally burn through 100 gallons in a weekend in your low compression engine, but that is irrelevant compared to the 200 gallons that a Navajo or big twin Cessna will burn through in a day, and consistently do so several days per week.

Most of the big consumers are operating engines that need the higher octane fuel. Navajos, twin Cessnas, P-Barons, and high-powered naturally aspirated aircraft all need it, and those are the big consumers. The general rule of thumb we use is 20% of the fleet burns 80% of the fuel, and that fleet could not use the 80/87 that the low powered aircraft could use without major alterations that would significantly reduce performance while increasing fuel consumption.

Lower octane fuel was removed from market because the demand did not exist for multiple fuels to be supported by the infrastructure. As it is, 100LL is in such low demand that the fuel companies consider it a "specialty chemical" rather than an actual fuel.
 
dmccormack said:
No problem...but what were the advantages of 100ll over the old 87 octane that required all GA airplanes to now use 100ll?
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Economics. They couldn't profitably produce, ship, store, and pump more than one grade, so they settled on the one grade that would work (albeit not perfectly) in all piston engines.
 
Bob Noel said:
To be more specific, it would be interesting to know what engines need 100LL, and what engines only would need, say, 94 octane fuel.
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Lycoming has a SI which covers that. I'm guessing Continental publishes similar info.
My own O-320 currently requires 100LL (by STC). I can no longer
use 80/87 or autogas.
Click to expand...
Check the SI -- your Lycoming engine is probably approved for 91/96, 94UL, etc, as well as 100LL.
 
Ted DuPuis said:
Dan,

You may occasionally burn through 100 gallons in a weekend in your low compression engine, but that is irrelevant compared to the 200 gallons that a Navajo or big twin Cessna will burn through in a day, and consistently do so several days per week.

Most of the big consumers are operating engines that need the higher octane fuel. Navajos, twin Cessnas, P-Barons, and high-powered naturally aspirated aircraft all need it, and those are the big consumers. The general rule of thumb we use is 20% of the fleet burns 80% of the fuel, and that fleet could not use the 80/87 that the low powered aircraft could use without major alterations that would significantly reduce performance while increasing fuel consumption.

Lower octane fuel was removed from market because the demand did not exist for multiple fuels to be supported by the infrastructure. As it is, 100LL is in such low demand that the fuel companies consider it a "specialty chemical" rather than an actual fuel.
Click to expand...


I fly other airplanes besides the Chief (which has an auto-gas STC, FWIW) which include an IO-520 and an IO-470 -- both over 200HP powerplants that were designed and run for many years on 80 octane until it was no longer available.

100LL has several times the lead of the fuel it replaced. GA is currently facing mounting pressure to reduce or even eliminate lead emissions. The vast majority of GA airplanes flying (including various twins) were designed and flown with 80/87 octane fuel.

Is there some reason why the market shifted to 100LL? Maybe some who owned and flew through the shift can explain the motivation?
 
gismo said:
Any engine that is turbocharged or has a compression ratio greater than about 7:1 requires more octane than is provided by Avgas 80. That includes most but not all injected (e.g. IO-360, IO-470) and quite a few carbureted large bore engines. I can't say what percentage of the fleet requires more octane than Avgas 80 but I'm certain it's substantial. And as someone already pointed out, the aircraft that need 100LL burn fuel at a much higher rate on the average than the ones that don't. I'll bet I can count the 65 HP four bangers at my airport that burn 50 or more gallons of fuel per month on one hand and still have four fingers and a thumb left over. And that's not because there aren't any, I personally know of at least 10 and I'm sure there's more I don't know of.
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I am not sure about your compression ratio comment... Even talking about cars, current compression ratios for cars requiring 87 octane are about 9.5-10.5:1. Cars designed to run on 'high octane' fuel (oft called 91, though 93 is available on the east coast) on the west coast run as high as 12.5:1.

In addition, at higher altitudes, it has been noticed that you can use much lower octane fuel without a knock problem.

The advantage to lower octane fuel, is it contains more energy, so you end up getting better performance.

Finally, I question that 70% figure. Is that 70% of engines that require 100 octane MECHANICALLY, or is that 70% that require 100 octane LEGALLY (as carded)?
 
Keane said:
I am not sure about your compression ratio comment... Even talking about cars, current compression ratios for cars requiring 87 octane are about 9.5-10.5:1. Cars designed to run on 'high octane' fuel (oft called 91, though 93 is available on the east coast) on the west coast run as high as 12.5:1.
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If we had their technology, we could do the same, but we don't, and for the existing fleet, won't even if the technology becomes available for new aircraft engines.
Finally, I question that 70% figure. Is that 70% of engines that require 100 octane MECHANICALLY, or is that 70% that require 100 octane LEGALLY (as carded)?
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My understanding is this is based on what the engines can use, i.e., the original certification values, not what's written on the wing today. And it's only 30% of the engines, not 70%, although they consume 70% of the avgas pumped in the USA (because they fly more hours and burn more gph than the planes which can run on less than 100 octane).
 
Keane said:
I am not sure about your compression ratio comment... Even talking about cars, current compression ratios for cars requiring 87 octane are about 9.5-10.5:1. Cars designed to run on 'high octane' fuel (oft called 91, though 93 is available on the east coast) on the west coast run as high as 12.5:1.

In addition, at higher altitudes, it has been noticed that you can use much lower octane fuel without a knock problem.

The advantage to lower octane fuel, is it contains more energy, so you end up getting better performance.

Finally, I question that 70% figure. Is that 70% of engines that require 100 octane MECHANICALLY, or is that 70% that require 100 octane LEGALLY (as carded)?
Click to expand...
Cars have variable spark timing and will (typically) retard the spark at full load (where you rarely run) to allow the use of higher compression ratios and best spark at lower loads (where they typically run) for better fuel economy. Many even have knock sensors that detect knock and retard the spark as necessary.

Apples, oranges.

In general how octane relates to energy depends on what you do to boost octane. I doubt that you will find that the energy content of high / low octane avgas significantly different - the octane rating is boosted by TEL as opposed to using oxygenates.
 
Keane said:
I am not sure about your compression ratio comment... Even talking about cars, current compression ratios for cars requiring 87 octane are about 9.5-10.5:1. Cars designed to run on 'high octane' fuel (oft called 91, though 93 is available on the east coast) on the west coast run as high as 12.5:1.
Click to expand...

I rented a Suzuki SX-4 that had a CR of 10.4:1 or something like that, and it required only regular unleaded. This is becoming fairly typical in auto engines. HOWEVER: These engine have knock sensors that adjust mixture and timing to stop or prevent detonation, and they also have rather small combustion chambers (cylinders) and higher RPMs, both of which are anti-detonation factors. Our big-jugged, slow-turning, fixed-timing, manual-mixture aircraft engines don't have any of that. They rely on intelligent operation, something that's getting rather scarce as younger generations have little idea or interest as to what goes on inside the machine.

As far as what aircraft or engines require 80 or 100 or 100LL, look them up in the TCDS section of the FAA website. Minimum fuel requirements are listed there.

Tetraethyl lead, as I understand it, is produced by one factory for the entire world market, in England. There is pressure to get this potential environmental nightmare shut down. TEL is hugely toxic.

Dan
 
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