avgas negatives?

[cujet]

There is quite a bit of misinformation about 100LL Avgas. I'll try to address some of this.

1) Avgas contains lead. However, recent modifications to 100LL (under the very same specification) have resulted in a product known as 100VLL (very low lead) It's what is generally available at Avgas pumps now. In other words, much of 100LL sold today is actually 100VLL.

2) Avgas is engineered to vaporize readily, for excellent cold and high altitude performance.

3) Avgas is high octane fuel.

4) Alcohol free unleaded has limited real world anti knock performance. Generally 93 is the maximum number, R+M/2. Without significant engineering, unleaded gasoline is incapable of higher octane. Swift fuels (a 100LL replacement) is an experimental high octane unleaded. It's not available.

5) Due to excellent vaporization, idle, low speed and high speed "jetting" may need to be adjusted slightly leaner with the use of 100LL.

6) Many high RPM engines exhibit a slight loss of power on 100LL. This is generally due to improper fuel/air mixture.

I use 100LL in all my yard equipment. It is trouble free. A perfect example is the lifespan of the primer bulbs on pump gas v 100LL. I have a 12 year old Echo blower with the original primer bulb at my aircraft hangar, still in perfect working order (avgas since new). Where my Echo weed eater at home has been through many primer bulbs with auto gas. I've now switched to 100LL in everything and my fuel system troubles have been eliminated.

Also, when properly tuned, 100LL just runs smoother in 2 strokes at low loads. Mostly due to vaporization issues.

 

[roger m]

I could be wrong mate but I think your octane ratings are in MON, not RON. I can't remember the conversion but I have a feeling your 92MON is about the same as our 98RON.

our fuel pumps here has decals that say octane is rated by r+m/2 method same as AKI or PON rating , but i believe you are correct i believe it would be 8-10 points less the way they advertise here,i thought you guys had better fuel,i guess everybody is in the same boat

 

[Sawin]

I've been running AV 100LL for a few years now. Haven't had any problems the would pertain to the fuel.

My son-in-law has a Dolmar 5100, that I have at my house for a while. He thought I should run it some because it had been at least two years since it has been started.

I did bring it into the heated shop to ck it out, but then put it on the tractor. Probably an hr. after that I used it. Temp was 10 -15 F. 4 Pulls and it was running. I have run it a few times now in the cold, and it has been fine.

 

[user 64030]

our fuel pumps here has decals that say octane is rated by r+m/2 method same as AKI or PON rating , but i believe you are correct i believe it would be 8-10 points less the way they advertise here,i thought you guys had better fuel,i guess everybody is in the same boat

High octane rating doesn't mean better fuel. It just means the fuel is better as resisting pre-ignition by having a higher flash point. There by supporting higher HP engines by allowing higher compression ratios, forced air power adders, and advanced timing. In all reality (and other things being equal) you should run the lowest octane the engine will run, without creating any spark knock.

In a saw if you increase compression (pop-ups, cutting squish) or advance the timing by moving spinning the flywheel, the saw you could benefit from (or require) the higher octane fuel.

Now since AV gas is does not suffer from some of the same EPA induced emissions reducing additives, and is FAA regulated to be ethanol free, it is probably a better fuel to run.

dw

 

[cujet]

One more thing. Avgas is consistent. It does not change from batch to batch, location to location or seasonally. So, once you are properly jetted and tuned, you are good to go. It's an advantage that is not possible with pump gas, as the blends change seasonally and the ethanol content varies. Giving inconsistent performance and making occasional re-jetting required.

 

[Gologit]

One more thing. Avgas is consistent. It does not change from batch to batch, location to location or seasonally. So, once you are properly jetted and tuned, you are good to go. It's an advantage that is not possible with pump gas, as the blends change seasonally and the ethanol content varies. Giving inconsistent performance and making occasional re-jetting required.

Well said. A lot of the guys I work with have switched to av-gas because of the consistency. Mo-gas, especially in California, is a real gamble. A lot of the smaller mom and pop stations aren't reliable in labeling their pumps and you never really know what you're getting.

We work at a wide range of elevations and other than the usual minor carb adjustments av-gas has given us better results than mo-gas. I haven't seen any unusual decrease in power at high elevation.

The slight extra cost of av-gas is more than offset by the reliability.

 

[wyk]

our fuel pumps here has decals that say octane is rated by r+m/2 method same as AKI or PON rating , but i believe you are correct i believe it would be 8-10 points less the way they advertise here,i thought you guys had better fuel,i guess everybody is in the same boat

It is 4-6 pts effective AKI difference depending on the rating, and who rates it(manufacturer-wise). 100 RON is roughly 95-96 AKI. According to Shell, their 100 "V Power" rated in Australia is 96 Octane rated via AKI. It's not available most places in the US, tho. But that is their rating. I have seen some 102 rated RON fuel in Europe break 98 octane AKI. And I have seen 105 at the pumps as well.

I was told by an engineer quite a while back(and I could be confused here, so take it with a grain of salt, I know I did - I was drinking a Margarita) in the late 60's or early 70's, the government forced the petrol companies/retailers to conform to the AKI ratings since there were multiple different ratings used at the time. This also standardized the minimum octane ratings as well to something like 86 or 87 AKI. Which is sort of sad, really. I have never seen lower than 90 AKI/95RON at the pump anywhere in Europe. This is nice because it allows higher compression in the 4 cylinder engines typical in your average car in Europe.

Now this all makes me wonder - why does Rotax suggest against using AVGAS in your 2 stroke Rotax engines? I mean, they give an explanation, but it doesn't seem to jive with what I am hearing here on AS:

http://www.rotaxservice.com/rotax_tips/rotax_feed2.htm

 

[user 64030]

....Now this all makes me wonder - why does Rotax suggest against using AVGAS in your 2 stroke Rotax engines? I mean, they give an explanation, but it doesn't seem to jive with what I am hearing here on AS:

Feeding your Rotax 2-stroke Aircraft Engine | Rotax fuel, Rotax octane, Rotax oil, 2-stroke oil

Lead does leave deposits, that is how it protected the un-hardened valve seats in the 4-stroke engines before unleaded fuels. It acts as a lubricant, but I guess a solid one, like graphite in a keyed, lock cylinder. Never thought of the deposits harming the bearings of 2-strokes, but lead is a metal, although the softest one I know of.

dw

 

[cujet]

Lead does leave deposits, that is how it protected the un-hardened valve seats in the 4-stroke engines before unleaded fuels. It acts as a lubricant, but I guess a solid one, like graphite in a keyed, lock cylinder. Never thought of the deposits harming the bearings of 2-strokes, but lead is a metal, although the softest one I know of.

dw

FYI, the switch from leaded to unleaded fuels in the 2 stroke GP bikes resulted in a serious reduction in crankshaft bearing life. In fact, the elimination of lead was the catalyst for the development of significantly better 2 stroke oils. The EG-D oils.

You won't find significant deposits when using Avgas. It burns clean and scavenges well. The use of Avgas with a quality synthetic oil will result in a very clean combustion chamber, and zero muffler deposits. However, lead fouling of sparkplugs can happen with long periods of low loads. It's rather rare now, with the 100VLL.

 

[MCW]

I've been running AV 100LL for a few years now. Haven't had any problems the would pertain to the fuel.

My son-in-law has a Dolmar 5100, that I have at my house for a while. He thought I should run it some because it had been at least two years since it has been started.

I did bring it into the heated shop to ck it out, but then put it on the tractor. Probably an hr. after that I used it. Temp was 10 -15 F. 4 Pulls and it was running. I have run it a few times now in the cold, and it has been fine.

That's not the fuel silly but because it's a Dolmar

our fuel pumps here has decals that say octane is rated by r+m/2 method same as AKI or PON rating , but i believe you are correct i believe it would be 8-10 points less the way they advertise here,i thought you guys had better fuel,i guess everybody is in the same boat

By the sounds of it we have less of an issue with ethanol here but the gubberment is slowly trying to push it in. Otherwise I'm sure we are pretty well all in the same boat. Also the higher quality fuel the better performance and efficiency we can gain from engines of all types.

 

[weimedog]

Now this all makes me wonder - why does Rotax suggest against using AVGAS in your 2 stroke Rotax engines? I mean, they give an explanation, but it doesn't seem to jive with what I am hearing here on AS:

Feeding your Rotax 2-stroke Aircraft Engine | Rotax fuel, Rotax octane, Rotax oil, 2-stroke oil

If you have ever worked on an old airplane motor and see all the grey in the exhaust....that,s residue from the lead in 100LL. 100LL is sort of the lowest common denominator for that market as there are some very old airplanes still in service and 100LL actually allows some of that ancient iron to still safely fly. Part from the soft valve guide issue as already has been articulated and part because the higher octane allows a larger range of variation in things like ignition timing and compression...there are SO many configurations in that world! AND as those things have to deal with altitude related issues, there have been a variety of solutions such as Manual ignition timing, turbo's..all kinds of things that a high quality high octane fuel can help reduce potential issues from both human error and design limitations. SO when the small airports have to carry fuel, 100LL is what they typically carry.

(Interesting there is a tax reason as well...in NYS you can't have a fuel island with Automotive fuel and AV gas...its a big issue as they are taxed and dealt with by the NYS-IRS in different ways..big fine! The local County Airport sold "Mo-Gas 87" and "100LL" until their lawyer got a call)

I have run AV Gas 100LL on and off for a long time. I ran it in my saws when I was milling in particular. That old 797 ran cooler with the 100LL and survived while I built seven horse stalls with Hard Maple and Ash milled with that rig. I've run 100LL in my old Vintage Race bikes, a 1982 Husqvarna 420XC and 1979 KTM MC80 420 (MX version) I do see that "grey" in the exhaust but have never seen any deposits of any kind in the lower ends of those machines ..or from any of the saws I've tore down after running 100LL. My guess Rotax has to also be cautious because of this litigious world and the applications they will be in and shoot for worst case scenarios. If it was a real issue...they would definitively say don't use it. I do wonder if fuel was allowed to settle and evaporate in a lower end..wouldn't it have to leave something behind? Make your last tank automotive no lead before storing a machine?

 

[cujet]

1) If you have ever worked on an old airplane motor and see all the grey in the exhaust....that,s residue from the lead in 100LL.

2) I do wonder if fuel was allowed to settle and evaporate in a lower end..wouldn't it have to leave something behind? Make your last tank automotive no lead before storing a machine?

1) Answer, in most areas, the recent reduction in 100LL's lead content results in far less gray in the exhaust pipe. While some areas may still have the higher lead content, it's being phased out rapidly. My personal aircraft, a Cessna 177RG, run on 100LL, won't have gray deposits in the pipe very often anymore. Mostly black now. In fact, it's been at least 6 months since I've had a batch of 100LL that left gray deposits. 100VLL (very low lead) is the norm now, and it's an excellent fuel, and it's still branded as 100LL.

2) 100LL is a great fuel for storage. It evaporates without leaving significant deposits, other than a hint of blue dye and won't varnish or gum up. In fact, it's specified to be good for at least 5 years in storage. There are compelling reasons to use 100LL as a storage fuel and in equipment that does not see regular use.

While the spec for 100LL calls for about 2 grams TEL/gal, the reality is that it contains less, and has been trending that way for quite some time.

Here is a quick bit of info on 100LL/100VLL. (it's the same stuff today)

FAA OKs use of 100VLL fuel for GA aircraft

 

[weimedog]

1) My personal aircraft, a Cessna 177RG, run on 100LL, won't have gray deposits in the pipe very often anymore. Mostly black now. In fact, it's been at least 6 months since I've had a batch of 100LL that left gray deposits. 100VLL (very low lead) is the norm now, and it's an excellent fuel, and it's still branded as 100LL. be good for at least 5 years in storage. There are compelling reasons to use 100LL as a storage fuel and in equipment that does not see regular use.
Here is a quick bit of info on 100LL/100VLL. (it's the same stuff today)

good to know! Maybe I'll go back to using even more...especially on the compression enhanced saws..thanks for the update. ( Would you know if "N03" has the new 100VLL at their two pumps? Is there a listing of places that do? Or is it still by chance.)

PS: You the cujet of Dirtrider.net fame? KTM type?

 

[Ambull]

The lead is bad for plugs (although I haven't seen it), bad for the environment, and bad for catalytic converters, but it does add lubricity to the mix. Old saws were designed to run on leaded gas anyway. I would bet that 100LL AVgas could extend the life of a piston and cylinder even when compared to non-ethanol unleaded gas.

However, after reading the Rotax info, the lead could lead to deposits on crankshaft bearings......causing premature failure. Haven't seen that yet either.

 

[cujet]

good to know! Maybe I'll go back to using even more...especially on the compression enhanced saws..thanks for the update. ( Would you know if "N03" has the new 100VLL at their two pumps? Is there a listing of places that do? Or is it still by chance.)

PS: You the cujet of Dirtrider.net fame? KTM type?

Yup, cujet from Dirtrider

No listing that I know of for 100VLL. However, I'd be surprised if your local pump was not 100VLL. It's been the norm for quite some time now.

Please understand, I'm not making the claim that 100LL is better in a performance engine than top quality leaded race fuel. There are certainly some fantastic leaded race fuels. In fact, it's known that certain fuels improve throttle response considerably.

Just that 100LL is a very high quality fuel, with known properties. It also lasts a very, very long time. I've flown on 5 year old fuel and it looked/smelled new and performed perfectly. I had some 100LL in my shed for 9 years as generator back up fuel. It was still perfect too.

 

[Nitroman]

I ran it in a Mc.-450 one tank after another , about a gallon and a half not letting the saw cool down much and it ran GREAT
I adj. carb. a little but not too much ,(a little richer) the old mac. seemed to run with good power , but i am still unsure:msp_confused: due to this thread i am going to use it in more of my saws .
A fellow at a saw shop went to a factory training seminar(sthil) they told him that it would eventualy cause a heat seizure,
boy was i thrown for a loop then. the companys today are trying to push canned gas on us i supose..
we can still get non- ethanol gas around here but i do not know how long it will last.
Most of my collection is saws from fortys-thru the sixtys.. any input on this also:msp_confused: david

Male bovine feces.

 

[sawmandave]

Male bovine feces.

HMMM does your wen electric chainsaw run on gasoline,, this might be a hard one for u to figure out!!!!!!!!

 

[wyk]

I tried some AVGAS in my Greyhound to see if she would run faster. I don't think it worked. And the deposits she makes are not remotely gray. Which is sort of odd, being she's a Greyhound.

[video=youtube;fX1RZTSAdcg]http://www.youtube.com/watch?v=fX1RZTSAdcg[/video]

 

[J.W Younger]

All in all i see more pos than neg with avgas. In the past 5 gal at a time was the norm but 15 from now on since i don't go by the airport daily. The non ethanol I tried was stale when
pumped cause its about a dime more a gal and they don't sell a lot. I burn 15-20 gal a yr in my saws.
The canned stuff is too expensive. Also the avgas can be stored and used in my generators if a power outage like back in 2k made pump gas unavailable for a week. I sure ani't tellin others to run it but for my purpose it makes sense.

 

[oneoldbanjo]

I used Avgas100LL for a year, and as most have acknowledged there is some good and some bad issues.

Good: It keeps for a very long time, doesn't gum up carbs or dissolve rubber, and my equipment is ready to start anytime. I have a generator with a fixed jet carb that was made before E10 fuel and it runs lean with the new ethanol pump gas - but it runs great on Avgas and it is always ready to start.

Bad: It takes me a minimum of an hour round trip to go get it. Even with careful adjustments my saws just don't idle as smoothly. And once you lean the saw out to adjust for the use of Avgas you have to be careful not to put a fuel mix of pump gas in the saw without adjusting the carb to run richer. (I put the tach on my MS361 with normal fuel and then checked it with Avgas and the saw had dropped 1,000 rpm with the richer running Avgas).


In response to this thread posted earlier - My belief is that those people who see fouling are not doing any mixture adjustements and running their engines too rich on Avgas.


Originally Posted by timmcat
I've seen alot of fouled plugs both 2s and 4s from people using AV gas. I'd use any of the non ethanol blends from Dixie products or VP before I bought any AV fuel.

I wonder how that is possible when I have run the stuff for years and haven't even changed a spark plug on any of the saws, LOL.

Such variances just baffle me.

l