100 Octane LL AV Gas
 

Yesterday was the first time I have used the above. At first my car ran great then started acting as if the carb had trash in it. Would not idle well just generally ran crummy. I then went and put in an equal amount of 93 octane from the pump drove it around and it cleaned up ran well. I did run it up to around 5 grand a few times because I was suspect that the carb had perhaps loaded up or I was fouling a plug. Not sure what was going on. Anyone have similar issues with running straight AV Gas?
I was driving my 67 Vette L79.

I've read AV Gas is formulated for lower oxygen content experienced at higher elevations. Not sure if that is true, but would explain it not running well at lower elevations. Seems a mix like you did of pump and AV Gas is more appropriate given you don't need that octane level for a typical high compression street car. Too much octane is not a good thing if you don't require it

I use AvGas quite a bit for the high compression BB. It is relatively cheaper compared to race gas, lasts forever (no ethanol breakdown). What I find is that when it is very warm out, it can idle a bit wonky (I have a stock 11:1 L78, all timing in at 3k). A splash of 93 can help there as you did. I also find that if you are running a stock Holley, it needs to be squeaky clean. I regularly pull the idle screws on the metering block and blow the idle circuits out with an air blast (Thx to Eric Jackson for that tip), change the brass filters regularly as well. With all that, my engine responds pretty well with AvGas

I use 100LL in my Z and it runs great. Have had not idle issues at all since using it.

My home is at 981 feet and my office (only 18 miles away) is at 1204 feet.

Av fuel is lighter than pump gas ( more liquidy) meaning more fuel entering & larger jetting needed if used pure. Lower gravity than pump fuel (density) means you actually run leaner with same jetting.i used it a lot mixed 50 50 with shell & worked good for me as witnessed by checking burn on spark plug. My experience any way.

100 Octane LL...
 

I started using this stuff about 15 years ago in snowmobiles...had to increase the jet sizes in both sleds. AV gas is designed to not absorb moisture...water in an airplane fuel system will hasten the use of parachutes. :shocked:

Blending it with some 93 non-ethanol high test is a good idea...or if you feel wealthy a little high octane race gas.

Our L78 cars seem to run pretty good with it...of course all big block cars go faster on the flat roads of Long Island :rolleyes2:

Ditto on what Tommyboy stated, and advantage to AvGas is minimal water absorb and NO ETHANOL, wont rot rubber that is not compatible with the Ethy garbage. If anybody on Long Island needs a steady supply/readily available at any time, ping me

Agree with the mix with AV gas. Use Shell V-Power Nitro 93 octane. No ethanol garbage in this gas.

Just a thought but could it be that you don't have enough compression for the higher octane?

I am at sea level and based on what you guys have said above, I think it was more of a carb setup issue for this fuel. You guys confirmed too that once I added the pump 93 things straightened out. Compression is 11.1 so may have enough compression? Can't answer that one.

What about the fact that AV Gas contains lead while Gasoline doesn't?

It does have small amount of lead (which will destroy cat converters if equipped). Although you have 11:1 compression, you have to figure in timing (if deviating from stock) as well. This could cause an increase in detonation, requiring more octane

I used to mix it 50/50 with 93, now I run it straight and have a carb set up for it when I go to the track, I use another carb and 93 on the street

Highly unlikely, I’m a pilot as well as a racer , I’ve used AV gas in many race cars and even some of my street cars at the track never had an issue like that. I’d guess you had some crap in the tank that made its way to the needle and seat and hung it open causing a nasty rich condition from the vent tubes flowing fuel out the top. Holley? ( just a guess but common)

For those running AV gas 100LL now stock up cause it’s going away very soon. The new unleaded AV gas has been approved. Pilots are not happy about the change over I can tell you that but 100LL despite its name actually has a lot of lead in it. So it’s gone.

Keep in mind that Aviation engjnes run at about 2600 rpm’s and this fuel is designed to run that RPM sustained more than 1000 to 6000 Rpms that being said it’s always run well for my cars and lots of landscaping equipment without changes.

Many lycoming engines running av gas are low 7.9 compression. Sometimes as low as 7.0! Big bore engines.

Thought some of you may enjoy this read about AV gas and of course none of us use AV gas on the street because that would be illegal. This information on AV gas is for off-road / track purposes only

https://www.aviationsafetymagazine.c...urn-baby-burn/

I never had any problems using straight AV gas years back. My Chevelle ran just find.

I do run a 50/50 93/AvGas mix in my old 911, has a 9:1 ratio, but high RPM. It runs VERY well on this fuel set up

I ran it with Sunoco Ultra 94 … Had good results…

I had a higher compression Buick and it would ping like crazy on regular 93, putting 5 gallons of av gas to a tank eliminated the ping and never an issue with the carb.
I also ran it in my outboard drag boat with zero issues. I was told that the rating of 100 octane was a min rating and it could see higher numbers.

Perhaps there was trash in the needle and seat that I picked up from the hand held gas tank? I am familiar with the issues that trash causes in a needle and seat and my issue did appear that was the problem. I was of the mind set that I was going to have to pull the carb and clean it. But when I put the 93 in the tank and ran the engine up to 5K twice things started getting better? Perhaps I was just lucky and cleared the trash? Right now the car is running like a top and I love the smell of the AV gas.
Here in Sarasota County I can get Sunoco 90 and 100 octane non ethanol at the pump. Will likely just use that simply because of ease of filling the tank. Prior to the AV gas this is what I was running, but just wanted to try the AV Gas.

We have a very small Sunoco gas station here in town, owned by a Retired Hot Rodder I'm told, only works on vintage cars and sells nothing but Sunoco Unleaded Race Fuels at the pump, last time I checked, 100 Oct Unleaded was about $10/gal. Can get AvGAs for around $6.75-7/gal

$10 a gallon is not bad. I pay 24 a gallon for 50:1 2cycle premix so I would love to have that gas station near me

I used 100LL in my 69 L72 Bel Air last year exclusively with no issues. Maybe a splash of 93 here or there, but at least 90% straight 100LL at any time. Was almost half the price of VP110 and seemed to do just fine. Plan to use it again this summer and as many summers as I can still get it.

I went back to the Sunoco Station that sells 100 Octane put five gallons in my car that had a little bit of 93/AG left. The 100 Octane Sunoco was $9 per gallon car ran well.
The AG is $6.75 per gallon as I recall. I am going to confirm a clean can get five more gallons of AG and run that just to confirm it runs well in my car at sea level.

I run the 100 LL in my Z with no issues. I've been told to add a bit of Mystery Oil

I have tried the Mystery Oil and it seems like my carburetor doesn't like it. Maybe I was using too much oil. What ratio do you use?

Approximately 2oz to a tank. I also have good luck with the Tetraethyl Lead additive.

Octane Supreme from Wild Bill's

Although the AvGas solves the octane problem for me, one of the other primary reasons I use it is to avoid the ethanol, the stuff just disintegrates and is so destructive to vintage fuel systems

Here is some good reading on av gas and octane requirements/ratings.
From another forum:
VeryFastVeryFast Well-Known Member
JoinedMay 14, 2006 Posts263 RDC Crypto106 LocationArizona & Puerto Vallarta, MX Websitewww.RRMarkets.com
Aug 6, 2008
#15
Real info on Race Gas/Av Gas...

My experience comes from 7 years as the western states representative for 76 Race Fuel, Unocals 40 hours Advanced Products course, Working personally with Tim Wusz (senior performance products Rep for Unocal, Tim was responsible for Unocals race fuel development for 30+ years). I have also met and discussed fuels/motors with just about every engine builder in every facet of racing in the western United States. I also conducted Educational Seminars at the Fred L. Hartley Institute in Brea in which we would invite Engine Builders for a tour of Unocals testing facilities and do live octane tests on any gasoline they would choose to bring to the seminar. Included in the training we would demonstrate live tests how Distillation curve, Reid Vapor Pressure, Specific Gravity, Octane Rating, F;ashpoint, etc are conducted and the importance of these numbers. Some of you will remember me from contingency with my 76 Racing Gasoline hospitality trailer in the 1990's.

Through the 50's, 60's, 70's and 80's Av gas was the base product used for most racing "gasoline". VP, f&L, Turbo Blue, and Trick all used AV gas as the base product. They would buy a tanker (8000 gallons of Av Gas) than add other hydrocarbons/TetraEthylLead (TEL) to the base, drive around the block stopping and accelerating the truck/trailer until they felt the product was mixed well. Obviously this was not The Science™, but it worked for most racers only because most racers use a higher rated octane than they actually need.

In the mid to late 1990's VP graduated to buying there own base product and do there blending of products in a much better fashion. Turbo Blue and Trick have since been bought Sunoco and are blended by Sonoco. Trick was purchased by Phillips 66 and has continued to be blended by Phillips 66.

The only two companies I am aware of who "cracked" there own base product is Sunoco and 76. And as we all know, 76 race fuel is no longer available, leaving only one true manufacturer of Racing Gasoline....Sunoco.

AV Gas has a MOR (motor octane rating) of 96, R+M/2 rating of 100, and ROM (Research Octane Rating) of 106.

AV Gas is lighter than racing gasoline thus more fuel/larger jetting is required. Jetted correctly you should not experience a lean burn at WOT.

I would not use AV Gas as a cleaner. The amount of TEL (2 grams/gallon) and other hydrocarbons makes it extremely carcinogenic. Same goes for all other racing gasolines.

Shelf life is NOT better. The reason pump gas won't last as long is because street gas has extremely lightend hydrocarbons to help your car start and idle. Racing Gasoline does not have these light end hydrocarbons needed for idle and starting, hence the reason race motors start and idle poorly.

Av Gas is NOT designed for low RPM motors. AV Gas is designed to not detonate/preignite causing detination. This would be the same design as race fuel. If you compare the "distillation curve" of AV Gas to Race Gas, you will find they are almost identical. The "distillation curve" controls the speed of burn across the combustion chamber.

You will only "spit" gas out the exhaust pipes if you run to rich or include a supercharger/turbocharger on your engine and "overdrive" the blower. Example would be the bitchin flames you see at the starting line of a drag race on normally aspirated engines and the long flames you see on all "blown" engines.

The LEAD (TEL) added to AV Gas is to increase the octane rating only. All heads these days have harden valve seats. There is no need for lubrication of the valve seats. All engines have come with harden seats since the late 60's.

AV Gas is not formulated for High Altitude. and will have very little, if not any performance differences vs racing gasoline. On the other hand, commercial grade fuels (87, 89, 92) will definitely enhance your performance due to the commercial fuel being oxygenated. The Oxygen enhancers added to commercial fuel is only for California Smog laws.

Advancing timing on your motor will definitely help with AV Gas and Race Gas due to its slow burn characteristics. On the other hand, be careful if your running commercial grade gasoline, more timing can cause detonation/preignition quit quickly.

AV Gas does not go BAD faster. It is extremely consistent. The MOR is only 96, whereas Sunoco Purple or VP C12 is 104. A rating of 96 is good for up to 10:1 on Steel heads and 12:1 on Aluminum heads with water cooling. Air cooled motors run much hotter.

Buying a higher octane for a $20-50K motor is the cheapest insurance available.

Remember this...OCTANE is a measure of a fuels ability to resist detonation/preignition. The higher the Octane number, the slower the fuel burns. Technically speaking 87 Octane fuel will develop more power than 118 Octane fuel. With this said, you should see gains in throttle response and HP by mixing commercial fuel and AV Gas/Race Gas. You now have some light end Hydrocarbons for throttle response and heavy hydrocarbons/TEL for detonation resistance.

Bottom line... use the most consistent fuel you can find and create horsepower by moving as much air as possible though the combustion chamber.

I have no reason to be bias here as I have moved on to much greener pastures. See you on the race course.

Good Luck,
Steve Poole

Also:
https://warteraviation.com/wp-conten...VGAS-100LL.pdf

And:
https://www.thecarburetorshop.com/Octane.htm

Bob

That is the MOSt informative article with all the facts in one article.

Thx for posting

There’s a few things I don’t agree with in that article . One is it’s not formulated for low RPM that’s relative. Most lycoming engines run at WOT at 2700 ROM or less many 2100 ROMs on the take off roll. So what low RPM he’s taking about and what the High Rpm?

If it doesn’t last longer that’s news to the aviation and landscapers who use it specifically because it doesn’t gel up like regular fuels.
Also airplane engines have 7.0 to 7.9 to one compression in its most popular engines
MOR rating is only half the story as well when it comes to octane .
I’ve personally drained fuel from an airplane wing that sat for over 10 years that didn’t have a tinge of varnish smell or flakes to it.

Regarding the author's comment about 100LL not being formulated for low RPM, I think what needs to be considered is that when 100LL was created, Tetraethyl lead was the best option to increase the octane rating based on the technology available while meeting all other requirements of recip aviation engines. Your comment about typical GA aircraft engines is correct, (2700 rpm or less), but I think the other performance factors outweighed the operating RPM range during development.

Also, for me personally, Avgas provides other valuable advantages with the prime one being it does not "go bad" in engines/carburetors/fuel systems that sit for extended periods of time saving tons of time/money/effort/frustration. I for one am looking forward to mass distribution and availability of the new GAMI G100UL fuel which promises all the performance/characteristics of 100LL, but without the tetraethyl lead.

I agree with those point but previous author said that the 100ll didn’t have a longer shelf life.

Idk if I’m thrilled w the new fuel coming online personally promises promises, heard it before we heard that with ethanol being added to fuel it wouldn’t be any differnt then our fuel lines started disintegrating . That’s bad enough in my boat or my car but I don’t like to mess around w any changes in my airplane . It took some time to see the effects of ethanol too it wasn’t right away . I won’t be flying my kids for a while when the new fuel comes out that is all I know .

https://youtu.be/IV3dnLzthDA

Thought this would be a good video for this thread

I agree with the shelf life issue as well. As for race gas, I have experience with VP, cannot recall exactly which formula, but it did show signs of going bad in an un-opened 5 gallon can within a couple of years...an experience I've never had with 100LL.

As for the new G100UL, all we have to go by is the extensive testing performed by GAMI which far exceeded the FAA's requirements. True, time will tell, but all indications are positive with no ill effects. Whether we like it or not, 100LL is on the EPA's radar as the single largest source of lead emissions into the atmosphere and once approved unleaded aviation gasoline becomes readily available, the EPA will move quick to ban 100LL.

Also, the video link you posted is excellent...never knew the history behind tetraethyl lead and CFCs....thanks!

I've been running 100ll in my Chevelle basically since I got the car back on the road in 2012.



I dyno'ed the 496 in the Chevelle with 100ll and it ran flawlessly.


I've ran 100ll on the dyno numerous other times on other projects, each with 0 issues.


I've A/B/A compared 100ll to 93 Sunoco premium in my Chevelle; on 100ll the car cold starts with minimal fuss and doesn't take much babying when it's cold before it builds enough heat to idle on its own. Idle characteristics are perfect. Hot re-starts are instantaneous. It is worth noting that the currently remaining 1/4 tank of 100ll in the car now is over 3 years old and it still starts and runs fine.



With 93, cold starts require quite a bit of throttle pumping and significant babysitting time when cold before it'll idle on its own. Hot re-starts require holding the throttle open +/- 1/3 and cranking until it starts, and idle quality is noticeably diminished. WOT performance seems to be fine, however.


An aside: combusted 93 octane stinks. 100ll smells fantastic.



Conversely, 93 octane feeding the 358" small block in my wagon is 100% uneventful, the car runs fine on it. Never tried 100ll in the wagon, don't see a need to at this point.


Lastly, I dyno'ed Albert Galdi's 950+ HP supercharged 540 on straight 91 octane fuel from a no-name gas station near the dyno facility. We ran it at 36° timing and +/- 160° water temp with just under 5 lbs. boost, air/fuel ratio was in the high 11's under WOT, and the engine ran perfectly with zero issues. The plugs came out looking absolutely perfect.


In a nutshell; the need for 100ll is somewhat application-specific, but in all the times I've used it in the last +/- 40 years, I've never had a problem with it.


My $.02, FWIW, YMMV.

For those who have purchased Avgas locally, I am assuming this is done at a local municipal airport. Are there any restrictions on the purchase?

I'm assuming it can only go into jerry cans versus directly into the tank of non aircraft. Same sort of restrictions as "off road" or "ag" diesel since there are no road taxes paid.

I go to a very small local municipal airport here on Long Island. Load up 3 or 4 jugs and leave. It has 2 options
1. typical gas station set up, slide your card, punch in how many gallons or $$ amount you want, pump and leave
2. On occassion, the guy driving the fuel truck will offer it up cheaper than the self serve pump, which is even better

Driving up and pumping directly into a car is no bueno. As stated, no road taxes collected. They let the "fill up your jugs..." situation slide as you "could be bringing fuel to an airplane that is not able to taxi up to the fuel pumps..."
Either way, I love the stuff and glad it is still available.

AV Gas...
 

A few years back I would go to a local airport...park the truck and trailer. Go inside, tell the gal I needed fuel, she opened the gate and I drove down along side the runway to pump. They would fill my sleds direct in the tanks and fill the jugs, too. Pretty cool...

-wilma