Aviation gas

Has anyone tried 100 octane low lead in a super pro series, or other older large mac?

I undertand the system used to rate octane changed in the '70s giving us artificially high numbers for the fuel we are using now. I also hear there is an additive in 100LL intended to prevent vapor lock, which is one of the maladies the larger macs seem to suffer from occasionally.

Just curious if anyone has tried it, and what their results were.

Hi octane only helps if you suffer from preignition right? Otherwise it gives you the same ammount of power.

I'm mainly interested in some of the additives, but I understand something changed in octane parlance in the late '70s.

Well as far as additives, it's got lead in it. Low Lead means low lead, not no lead. Would lead hurt a saw? I'll try to check our manuals at work tonight, and see if I can get some specifics on avgas for you.

Take care all,
Jeff

I have done a little research, as near as I can tell, 100LL contains only 50% the TEL (lead) that automotive gas did. At the time most of my saws were released The pump gas was all leaded (with the exception of my 105..) but that still puts it in range for the octane rating change. But again, I am most interested in the additives they have in the fuel. They can't have planes vapor locking in air, and according to several people who (say they) know something, there are anti vapor lock additives. ?According to all theold hands around here, they say the bigger macs tend to vapor lock, which is not what I need while i'm humiliating a modern saw.

How will you get the aviation fuel? The small airport here will not sell it to just anyone that pulls up with a 5 gallon can.
Ray

That's good to hear about the lead being good in the saw. I was just wondering. I work nights so it'll be tomorrow that I get back to you, if I can find it in the manuals, and have time. We've got some scheduled maintenance tonight. And as far as aquiring the LL, if you don't already have a source, you could probably ask some of the general aviation guys at your local airport to save their fuel samples for you. Off the record, I've seen alot of fuel samples go in the trash, on the gound, in the lake (in the case of float planes) all over the place. I'm sure someone would be happy to fill a milk jug for you over the course of a week or so...just an idea.

Take care all,
Jeff

well, I have two buddies that fly, plus I have a last name that means something around here. I think i can get it.

Hariati be careful using Aviation fuel most are ashless and don't assist in preserving 2 stroke engines, after all chainsaws can't fly or do they ??

Bob

Lead is good for a motor it is a lubricant Also Av Gas is designed to build heat because planes run in much cooler conditions and if the motor wont run hot enough the carb could ice and planes dont like to fly slow So I would just stick to high grade pump gas

Good answer MacBoy : )

RC guys put saw motors on their large planes all the time.....so I guess technically the powerhead flies......



Travis

I actually have worked at an airport from time to time in my past..AND ALWAYS use 100LL in all my saws &two stroke motorcycles including the McCulloch 797. I also mix with Mobil One MX2T.

I use this in the mototcycles as well. Couple of things.

1) First time you do a plug check your going to be certain something is wrong...they come out lighter.
2) Every two stroke I have used this mix on run cooler than with even high test standard pump gas. Imperical data.
3) I can get more low end punch out of my motorcycles but loose a bit of top end power. I have no idea why but its a consistent thing. Especially my 1982 husqvarna. I can&have advanced the timing a bit and that excentuates that snap off the bottom feel on my motorcycles.
4) There are NO alcohol additives that attack diaphrams& fuel lines.
5) Lead additives are somewhat lubricants.
6) The quality of 100LL is better..less water, more consistent from load to load in density. I was involved with fuel deliveries a while ago and there is a difference in the "white bucket" tests &specifice gravity tests. After going thru a few "mo-gas" vs. "100LL" fuel deliveries ...I can't imagin why any person with an Aeroplane (or any motor you value..) would even consider "Mo-Gas"!! (Automotive quality fuel sold at airport..same as what you get at the corner store) Alway get water to settle out in the white bucket tests with "Mo-Gas"..BUT NEVER EVER have seen even the smallest drop of water in 100LL. I have seen lots of water in Automotive fuel with alcohol additives out west (not AV gas). The airports "Veeder - Root" tank monitoring system made it easy to keep track of the water build up in those tanks and they did get them cleaned when there is just a inch of so at the bottom...but it ALWAYS returned after a few more deliveries. (Since they draw the fuel from a foot or so off the bottom there NEVER is water in the filters at the pump which were checked weekly...but your corner store doesn't have those water trapping type filters the airports do either!).

My McCulloch is used for milling mostly...I can actually feel the difference in the heat coming off that motor (those who chainsaw mill can appreciate the close proxemity to that saw when bulling it through a 12-16ft log!!) when I was switching to Pump gas when I ran out of AV gas a few weekend back.

I have not seen any sign of piston/cylinder wall wear on that McCulloch 797...so either the Mobil One is working well or there is no problem using the AV gas or both.

Theory? Ash can it. Imperical data works for me.

macman101a said:

Also Av Gas is designed to build heat because planes run in much cooler conditions.

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Macman,

Not to pick on you, O.K. I guess I am picking on you. Based on what I know, and my experience, I would move your above statement into my trash bin. That is unless you can please supply some scientific info describing how aviation gas makes a 4 stroke engine ( good job huh.. Glen? ) hotter to any meaningful degree.

The burn rate of the fuel is slower wich in turn gives you more torque and also builds heat because the flame lasts longer that is why you lose top end power because the burn rate is for a low rpm motor planes run at a low rpm to keep the motor life and dependability up. Like diesel motors build lots of heat when under a load Bottom line its the BTU value the fuel has Take a look at VP Racing for more info

Here's what my brother (aircraft owner and A&P license) once told me about 100LL:

It does have a higher vapor pressure to help prevent vapor lock at altitude. And it also has stabilizers added since avgas does not have the high turnover rate of pump gas, avgas may be in the storage tank six months or more. He also said on the real old engines 86 octane was preferred, but since 100LL is more readily available you could use it.

Interestingly, for some aircraft engines you could "buy" a certification from the FAA to run pump gas. The cost was $.50 per horsepower, so his 200HP Continental would have cost him $100. He did run pump gas and said because of the lower vapor pressure it vaporized more readily & made engine starting easier especially in cold weather.

Are you sure MacBoy?

Look up fuel burn rate on none oxygenated fuels

macman101a said:

The burn rate of the fuel is slower wich in turn gives you more torque and also builds heat because the flame lasts longer that is why you lose top end power because the burn rate is for a low rpm motor planes run at a low rpm to keep the motor life and dependability up. Like diesel motors build lots of heat when under a load Bottom line its the BTU value the fuel has Take a look at VP Racing for more info

Click to expand...

Macman,

I have a bad cold you know.. Your killing me with your last posts, you know it really hurts to laugh! You need to go easy on me.

I really don't where to start, without coming across as condescending.

you should start I would like to hear it thanks Mike