100 octane low lead av gas

[jdsledman2001]

I read on here some where about not using 100 octane low lead airplane fuel. What is the reason for this? Just wondering I thought this maybe better then 93 octane with ethonal . Thanks

[400brian]

The ultralight aircraft guys run 100LL when nothing else is available. The modern 2 strokes they run are typically designed to run on regular. As I recall, they reported that 100LL gave them higher EGTs, more plug deposits, and no performance gain. Obviously the engine needs to be tuned, and have the compression, to take advantage of the higher octane. The stuff is pretty pricey too!

[MaxThrottle]

My family ran a small airport in upstate New York for decades. Essentially, free access to 100LL, SWEET !!!!!!
But here are some facts to consider. 100 LL (AVGAS) has about 4-5 times as much lead as regular LEADED gasoline (2 grams per gallon vs. 0.5 grams per gallon). Tetra Ethyl Lead (TEL) is added to increase the anti knock index of higher octane fuels to make them "more stable for combustion". AKA less detonation. Lead fouling of your plugs and higher EGTs will be the result of running 100LL.

Lead fouling usually appears as yellowish brown deposits on the insulator nose. This can not be detected by a resitsance tester at room temperature. Lead compounds combine at different temperatures. Those formed at 370-470°C (700-790°F) having the greatest influence on lead resistance.

If you insist upon running 100LL, there are additives that you can mix with 100LL to make it less prone to lead fouling. TCP ($34.85/Qt.) by ALCOR Chemical Company is one, but its tendency to be corrosive may have you rebuilding your fuel systems more often. Another is "RUN-UP" ($28.85/Qt.) fuel additive from DECALIN Chemical Company. Both are available from www.aircraftspruce.com

After changing a lot of lead fouled plugs. I just buy some good 89 Unleaded pump gas and some CD2 additive and have just as much fun. No problems in 15+ years.

[That Girl Racing]

Lower EGT readings maybe. Higher, absolutely not. In a stock sled a waste of money. Why not run premium unleaded?

[jdsledman2001]

That girl racing: My original question was if this was a good alternative to ethanol fuel. I realize I don't need 100 octane but I dont want fuel with ethanol in it, this is my only option in this area.

[TOYMECH]

JDsledman - As a possible alternative to using AV, stay with unleaded fuel and use an additive for prevention of negative effects of ethanol. I have had a lot of people into vintage sleds and vehicles tell me about how pleased they are with this product:

http://www.goldeagle.com/products/product3CC6.aspx

I just started using it in my sleds this season (for as much as they ran due to lack of snow) so i cannot tell you firsthand if it works well. They seem to start and behave very well with this added to the fuel, but i will not know till the fall when i pull my carbs to do yearly maintanence and cleaning. If it does work like thier regular fuel stablizer, it should be a good product as i have had good results with it in all small engines i have.

[That Girl Racing]

Okay. I'll bite. What is the problem with the ethanol/gas mix? Normally premium has less and except for going bad quickly I don't see any adverse effects from it.

[TOYMECH]

Ethanol = Moisture magnet. Ethanol = Highly oxygenated fuel = leaner air/fuel mixture.
Take a look at two comparable (displacement etc) competition engines. The one that uses "gasoline" is running a lot less (raw) fuel through it than an engine that burns straight methanol. That is a extreme comparison, however.
In the case of older snowmobile engines: They were engineered and thier fuel curves/calibration set up and tested to run gasoline NOT "gasohol" or gasoline/ethanol mix (which has a higher oxygen content than gasoline).
I worked as a small engine/marine mechanic back in the early 80's when gasoline was gasoline. Yes, we found shellac in carburetor bowls of poorly maintained units. Nowdays, talking to friends still active daily in the trade, they are finding a jelly-like substance left behind from gasoline/ethanol and corrosion and degredation of components like o-rings etc. A friend who works at a Toro dealer tells me there is updates and service bulletins constantly coming through for fuel systems because of the effects of ethanol.....

[That Girl Racing]

Doesn't seem to effect trail sleds that get thousands of miles on them. Definetly goes bad quick but if you put premium and stabiliser in the spring them they don't gum up. Go up a few sizes on the mains if you are worried. There was a lot of talk about ethanol a few years ago but once again the world did not come to an end.

[Joliet Jake]

I tried to lay off this post but when it comes to fuels I just can’t resist!!

When I was getting my pilots license I was schooled in the reason for the “RON+MON/2” or research octane number + motor octane number divided by two.
While I believe I wrote a post on this before, so I won’t go into it now.
But basically it was invented because world war one airplane engines would go into detonation and burn holes into their pistons on one batch of fuel and run fine on another batch that came from the same refinery.

One reason aviation fuel is so expensive is it is tested repeatedly and it must adhere to a very strict recipe for any additives. Traceability for every batch of fuel is also very costly.
Obviously you can understand an engine failure is a little more serious in an airplane!
By the way today 100 LL was 6.05 a gallon

Airplane engines by design, especially older ones use lead more or less as softener for the valve seats and guides { the molecules act like little rubber balls softening the effects of the valve springs slamming the valve closed} That’s why modern airplane and auto engines have stainless valve seats.

In recent years many airplane owners have tried running there engines on automotive fuels or Mogas.
These conversions had to be approved by the FAA, so the FAA has done a lot of research and what they found was there was such a diversity between what was advertised as far as octane and additives there would be problems.
So basically ,they allow it in some airplanes but issued a stern warning that they could not endorse it in others because of the poor quality of automotive gasoline.

In the old days you could by different grades of AV gas …IE 115/145 but now days general aviation gasoline is down to 100 low lead.
Because so many older airplanes are still flying and the benefits of leaded gasoline are so many it will be a slow to phase out of leaded fuel, but I have no doubt it will happen and we will see airplanes running on green fuels.

That Girl Racing ….
I really don’t see anything wrong with ethanol mix in auto fuel as long as you know what to expect.

But the way I have been taught is if you design an engine to run on gasoline oil mix your jetting is for gasoline that burns best at a ratio of 1:12.5 everything you add to that effectively leans the mixture!

If you add more oil than the manufactures suggested ratio……you have leaned the mixture
If you add ethanol that burns at a best ratio of 1:7.….. you have leaned the mixture.

Add to that the fact that ethanol is corrosive to aluminum magnesium and an rubber and the reason aircraft owners don’t use it …….it loves water and absorbs it like crazy!
But at ratio’s of 10% it probably won’t hurt a thing …….unless your on the edge with timing and jetting

Like it or not ethanol and other green fuels are here to stay!……… What we have to do is understand how these fuels act with our older machines.

[daisydukers]

If you add more oil than the manufactures suggested ratio……you have leaned the mixture

I thought adding more oil makes the mixture richer??? Or am I just confused once again...

[JD600]

Adding more oil makes the gas/oil ratio richer, but at the same time it makes the air/fuel leaner because it effectively dilutes the gasoline. I've never really given it a thought, but thats correct. On that note, What are your recommendations for break in if adding more oil leans the air/fuel ratio Peter?

DE

[That Girl Racing]

As with all trail sleds, Deeres are very rich from the factory. But............. more oil at any time makes more power.

[TOYMECH]

Interesting article here for all to read:

http://dirtbike.off-road.com/dirtbike/t ... 20502.html

[That Girl Racing]

I run the race sleds. 25/1 mineral based oil.