Any Drawbacks Of Av Gas?

[H20MOFO]

I Don't Know WHAT I'm Worried About Because I'm Still Workin On An Airport I Can Fill Up At. Haha I've Heard It's Better At High Altitude.(thats Me Utah) Just Worried About Tuning Issues,(higher Egt's) I Don't Need Straight Av Gas For My Set Up Just A Mix. As A Rule Would I Need To Change My Jetting?

[gbelt]

Avgas is very dry, if your going to use it mix it with some automotive fuel or add some marvel mystery oil to it. It's formulated differently because it's meant to run at higher altitudes but I think it works well, smells good too. It also lasts a lot longer sitting around than automotive gas.

[jimsplace]

AV gas is dry, meaning it does not have water in it. Water freezes at high altitude due to cold temperature. AV gas is formulated to perform from desert to high altitude and not vapor lock also.
Automotive fuel is formulated in contrast, to operate seasonally, that is for hot weather in summer, and cold in winter. The AV gas is more consistent throughout the year.
AV gas is much more consistent in performance than automotive gas. Aircraft may take off in the desert and land in the mountains. It must be capable of taking off and climbing to higher altitude rapidly where the air is thin and not boil off. Automotive fuel doe not require that characteristic, along with a number specific requirements.
AV gas does not have the higher octane of some of the race gases that may be required in some engines.

[Sleeper CP]

I think they answered the question.
If you mix 50/50 or even 2/1 with super unleaded you'll have enough lube to keep your fuel system healthy.
Sleeper CP
Big Inch Ford Lover

[H20MOFO]

Yep. Thanks All

[Rexone]

There's a lot of info on the forum on this subject. I've added some thread links to the bottom of the first post in Gear Heads Tech Links thread. Read through them and the links within them. Lots of info here.
http://www.***boat.com/forums/showthread.php?t=131437
http://www.***boat.com/forums/showthread.php?t=102391
http://www.***boat.com/forums/showthread.php?t=74624
http://www.***boat.com/forums/showthread.php?t=53599

[curtis73]

whoa guys... avgas has nothing to do with dry or wet. it has nothing to do with altitude. It doesn't matter what fuel you run, a 4000-ft change in altitude makes the same difference.
Avagas is simply a variation of gasoline. It is usually sold in many forms, but most commonly 101LL (meaning 101 octane, low lead). The octane rating varies depending on the predominant craft at the field and base altitude of the strip, but 101 is very common. Many fields refer to it as 100LL to be safe, but if its light bluish-green in color, its 101LL.
It does not have anything to do with altitude. Planes operate at anything from sea level to 18,000 feet for single engine, more for larger craft. It has nothing to do with water. No gasoline has water in it, and if it does you should be calling a lawyer.
Avagas is simply a different formulation of gasoline that is more suited to aircraft. It is very similar to coleman fuel or white gas.
If you decide to run it in a boat or car, go ahead. Its great stuff, but you have to completely retune the carb or EFI to run it. It is much lighter than gasoline. Whereas gasoline burns stoichiometrically at 14.7:1, avagas is more like 12:1. Simply burning avgas will cause the engine to run dangerously lean without any other changes.
Its no different than changing from gasoline to ethanol. You have to recurve the fuel system, but it has nothing to do with altitude or water. They are just different fuels, but they all have to follow the same laws of physics regardless of altitude or composition.
Aircraft may take off in the desert and land in the mountains. It must be capable of taking off and climbing to higher altitude rapidly where the air is thin and not boil off.
That is not a function of the fuel, that is a function of the pilot altering the fuel curve based on altitude and barometric pressure. Avgas is not used anywhere near an altitude that boiling is even considered. In fact, the pilot is responsible for adding carb heat to prevent icing if the fuel in the carbs. If you're burning avgas, you're not really any higher than a car could get in the Rocky Mountains. I don't recall any of my cars boiling their fuel when I was in Vail or Santa Fe.
There are knobs on the dash to alter fuel curve and carb heat. It is the PILOT'S job to compensate for altitued and temperature, not the fuel. Airplane engines fall under the same physical laws as automotive engines. It doesn't matter what fuel is used, the atmospheric laws remain the same.

[curtis73]

I Don't Know WHAT I'm Worried About Because I'm Still Workin On An Airport I Can Fill Up At. Haha I've Heard It's Better At High Altitude.(thats Me Utah) Just Worried About Tuning Issues,(higher Egt's) I Don't Need Straight Av Gas For My Set Up Just A Mix. As A Rule Would I Need To Change My Jetting?
Yes, absolutely you need to change your jetting. Think of avgas as a lighter gasoline.
Just run gasoline. Its way cheaper, and for 90% of your altitude changes you don't need to worry about jet changes. I've run many engines between sea level and 8000 ft, and they run a little rich at the high altitudes, but not enough to worry about.
Put it this way, you could retune it for high altitude on gasoline, or you could retune it for high altitude on avgas. Why change fuels to get the same thing? Just burn gasoline and don't worry about it.

[jimsplace]

Perhaps I did not go into sufficient detail on the "boiling off" point. But yes, that is a factor.
I will quote from Chevron: "An aircraft taking off from sea level with fuel temperature at 100 degrees and ascending rapidly to 20,000 feet may experience vapor pressure that is greater than the pressure in the fuel tank, i.e., the fuel will boil." As a further clarification, atmospheric pressure drops to 46 percent of that of sea level value. I.E., liquids boil at
lower temperatures at higher altitudes.
AV gas is held to much higher standard on water content than automotive gas (pump). Water comes from condensation, rain leakage, even some of the process used in production create water. The AV gas is filtered and checked frequently for this problem. That is part of the reason we should use fuel/water separators (filter) with our fuel system.
There is an excellent publication from Chevron. It is Aviation Fuels - Technical Review.

[H20MOFO]

I was just wanting to save some coin, 110=$6.20 av gas I was told was $3.25 ish. I'm guessing a little but i think i need around 95 octaine, and the best pump gas around here is 91. All good info. Thanks again.

[Sleek-Jet]

That is not a function of the fuel, that is a function of the pilot altering the fuel curve based on altitude and barometric pressure. Avgas is not used anywhere near an altitude that boiling is even considered. In fact, the pilot is responsible for adding carb heat to prevent icing if the fuel in the carbs. If you're burning avgas, you're not really any higher than a car could get in the Rocky Mountains. I don't recall any of my cars boiling their fuel when I was in Vail or Santa Fe.
There are knobs on the dash to alter fuel curve and carb heat. It is the PILOT'S job to compensate for altitued and temperature, not the fuel. Airplane engines fall under the same physical laws as automotive engines. It doesn't matter what fuel is used, the atmospheric laws remain the same.
Not quite.
Carb heat is for warming the intake air enough to keep ice from forming in the venturi of the carburator. It has nothing to do with the temperature of the fuel. For those that aren't familiar with airplanes, airplane carbs are mounted below the engine, so they don't get warmed by the engine's heat like automotive carbs do. So they will ice up do to the temperature drop through the venturi. Once ice forms, the venturi action is reduced and the fuel can no longer combine with the intake air... silence quickly follows.
Fuel injected aviation engines don't have carb heat, since the combining of fuel and air doesn't rely on venturi action.

[centerhill condor]

silence quickly follows.
and then prayers and screams..:)
CC

[Boostedballs]

I love AVgas!
AVgas is mandated by the FAA, it has to be able to run hi compression air-cooled engines, AND it has shelf life requirements that regular gas does not. I was told that it is safe up to 2 years! It needs to be. Imagine you just pulled your Cesna out of the hanger after it sat for 8 months and you want to fly to Reno. 8 month old gasoline would be sticking to your intake valve stems until they stick and you go crashing into a school yard.
If you run AVgas, you won't have to drain your fuel system for storage. Great for boats!
I run it in everything from my rally car to my lawn equipment. I think it even runs a little smoother than gas. I don't have to worry about messing with my chainsaws etc when I pull them out in the spring. Just pull the rope! You will have to richen up the carbs a bit when you first start using it though.
I run 20psi in my turbocharged rally car on that stuff with no problems. I would rather run Trick or VP, but I'm not about to pay $40 for 5 gallons! And AVgas smells oh so sweet!

[H20MOFO]

thanks boosted.

[IMPATIENT 1]

been runnin avgas for yrs, with no ill effects.i do run 25% super unleaded, and you'll want to jet up till a/f ration is good(or plugs like nice).

[bigblockbill]

Avagas is simply a variation of gasoline. It is usually sold in many forms, but most commonly 101LL (meaning 101 octane, low lead). The octane rating varies depending on the predominant craft at the field and base altitude of the strip, but 101 is very common. Many fields refer to it as 100LL to be safe, but if its light bluish-green in color, its 101LL.
I was thinking that the 100LL or 101LL was not relivant on the auto octane levels. ie 100LL does not mean 100 octane. The scales are different from what I have been told and that 100LL by the "auto" octane scales is more like 114 or so.
The problem with trying to mix it with pump gas is you never get the same ratios (unless your carefull which most of us are not) and then end up effecting your jetting. Seems like the same motor on pump gas typically runs 3-4 jet sizes leaner than 100% AV. If your carefull to keep the same ratio of AV then mixing it with pump gas works great.
If your running AV straight just mix it with some Marville Mystry Oil and the carb will stay nice and clean.

[gbelt]

They are rated a little differently, used to be they had two numbers, a lean octane rating and a rich octane rating. The 100 in 100LL will be for the lean mixture at altitude, the other number would have been for low altitude/full rich mixture as would be used on takeoff and was usually around 130. I shouldn't have mentioned dry in my first post, what I wanted to get at is that avgas has different lubricants in it than auto gas does, aircraft parts tend to be high quality metals for obvious reasons and as such have different lubricataion requirements, if you don't think the gas is that different get some on your hands, it will dry them out and not leave the oily residue that auto gas does, smells more like laquer thinner and has that sweet exhaust smell. When I used to flight instruct I used it all the time in my boat, and my old cars since I had access to it, they all ran better IMO, although since they all have Holley carbs they tended to run a little rich anyhow. If thats all your running then yes, you need to jet up, and also add some lubricant such as Marvel Mystery oil. It's been a while but compression on most of the GA engines I've seen ran between 7.5 and 8.5:1. They are much like a boat engine when running since they are under a load most of time.

[biggraypig]

A lot of the smaller airports in Utah you can pull right up to the pump stick in you credit card and fill er up. My buddy does it for his race car all the time.

[palhal]

Years ago I ran AV gas in a stock boat eng and burn't a hole in the top of a piston in an hours time. Started mixing 1/2 automotive gas with the AV gas with good results.-----PALHAL

[HOWARD UFH]

I may be a little lost,why would you need to ad lube to the av-gas isnt methanol not lubricated?

[jimsplace]

I would like to add to HOWARD UFH, How about propane and natural gas motors. Is there any lubrication there too.

[Sleeper CP]

I would like to add to HOWARD UFH, How about propane and natural gas motors. Is there any lubrication there too.
The lube helps the fuel lines from drying out after use. It also doesn't hurt the fuel pump seals and regulator gaskets either.
If you pour av gas on your hand when it dries it damn near makes your skin crack.
Sleeper CP
Big Inch Ford Lover

[MEANSTREAK]

Can anybody tell me the true octane of 100LL AV-GAS?

[Sleeper CP]

Can anybody tell me the true octane of 100LL AV-GAS?
That depends. I just googled "octane rating of 100ll Avgas" you should do the same. There is a Wikiapedia article there that is pretty good.
Sleeper CP

[GofastRacer]

Besides being a good lubricant in Avgas, Marvel is also a great leak detector!..

[H20MOFO]

Vacume or oil leak. Please explain.

[Sleeper CP]

Vacume or oil leak. Please explain.
Neither.
FYI, Leaks in the fuel system.
Sleeper CP

[H20MOFO]

I think if I (or anyone) had a fuel leak you'd know it. Is marvel brightly colored or something? Also where do you buy marvel?

[396_WAYS_TO_SPIT]

I think if I (or anyone) had a fuel leak you'd know it. Is marvel brightly colored or something? Also where do you buy marvel?
It has a redish tint to it. You can buy it at Car Quest,Autozone,Checker Auto,Napa,etc

[jimsplace]

When I have a fuel leak with av gas, I get a blue residue without any oil.

[Sleek-Jet]

When I have a fuel leak with av gas, I get a blue residue without any oil.
The blue residue is the dye they use to tint the gas. It's sticky and a pain in the ass to get off, but the leak is always plainly visable.
You shouldn't be putting enough MMO in to change the color of the gasoline... :jawdrop:

[GofastRacer]

I think if I (or anyone) had a fuel leak you'd know it.
I would you know if it's just seeping, it evaporates too quick!

[GofastRacer]

The blue residue is the dye they use to tint the gas. It's sticky and a pain in the ass to get off, but the leak is always plainly visable.
You shouldn't be putting enough MMO in to change the color of the gasoline... :jawdrop:
If you mix it 50/50 that dye that dye is just about gone though!..
Marvel says 4 ounces per 10 gal but it's kinda oily, 3 seems to work pretty good, keeps the shrottle shafts from squeeking!..