Using AVgas in your small engines

subcamper wrote:

Kemahsabe wrote:
The owner of a local outboard motor repair shop told a group of us that we'll have fewer fuel-based problems in small engines using 100LL. A member of the group has had a lot of small engine problems at his remote ranch in west Texas. So he went to the local airport and bought 5 gallons of av gas.

None of the engines he tried ran right, or would run at all, on that gas. He had to drain it out and replace it with plain old auto gas. Everything started and ran fine. No idea why that would happen. Plan to ask the outboard motor expert next time I see him.

Despite rumors to the contrary, high-octane fuel is not "more powerful". The higher the octane the HARDER it is for the fuel to ignite. High-octane fuel is needed in higher-compression engines to prevent pre-ignition ("ping"). In other words, the gas ignites too soon, before TDC which causes the piston to push down while it is still going up toward TDC (bad situation). Also, engines using high-octane fuel can advance the timing to get more power (and sometimes better fuel economy).

Small engines will often not run on high-octane fuel because there is not enough compression to ignite the fuel. A friend bought a new Sears lawnmower a few years ago and it would not start. He called me over and I checked everything (spark, fuel going to carb, etc) but it stoill would not start. Finally, he said he got some premium gas and put it in when he bought it. We dumped the premium and put in regular and it started and ran fine.

Steve

That could be the answer. Makes sense. Thx.

Having operated an Alkylation plant at Shell Oil Co Martinez refinery (LOP) I can tell you the engineers worship the characteristics of "alkylate" a main component of avgas.

Made from Isobutane, alkylate is a liquid. Has ZERO sulfur or heavy ends in it. By itself has near 100 R/M / 2 octane. Stores for a long long time with zero decomposition. Can be used STRAIGHT and PURE in a gasoline engine and the engine loves it - school of hard knocks with a 12.5 to 1 compression ratio engine.

AVgas is an exotic blend I never had anything to do refining the various grades. But TEL handling is scary. Tetra-ethyl lead is a liquid. Dark. We had to dress in HazMat-like suits. 100% coverage. Filters to breathe. We were scolded without mercy. "One single solitary drop of TEL on your skin and you are dead! No first aid, no treatment, and it cannot be washed off fast enough!"

Scared the hell out of one 20-year old student working in LOP for the summer!

But please be careful around 100LL. It's only called Low Lead because other grades of avfuel contained insanely high amounts of TEL. 100LL contains more TEL than car gasolines Chevron Custom Supreme, or Sunoco 260, ever did.

100 LL on the skin and TEL is absorbed. I would not touch the stuff myself without using gloves. Tetra Ethyl Lead poisoning is bad Juju.

Kemahsabe wrote:
The owner of a local outboard motor repair shop told a group of us that we'll have fewer fuel-based problems in small engines using 100LL. A member of the group has had a lot of small engine problems at his remote ranch in west Texas. So he went to the local airport and bought 5 gallons of av gas.

None of the engines he tried ran right, or would run at all, on that gas. He had to drain it out and replace it with plain old auto gas. Everything started and ran fine. No idea why that would happen. Plan to ask the outboard motor expert next time I see him.

Despite rumors to the contrary, high-octane fuel is not "more powerful". The higher the octane the HARDER it is for the fuel to ignite. High-octane fuel is needed in higher-compression engines to prevent pre-ignition ("ping"). In other words, the gas ignites too soon, before TDC which causes the piston to push down while it is still going up toward TDC (bad situation). Also, engines using high-octane fuel can advance the timing to get more power (and sometimes better fuel economy).

Small engines will often not run on high-octane fuel because there is not enough compression to ignite the fuel. A friend bought a new Sears lawnmower a few years ago and it would not start. He called me over and I checked everything (spark, fuel going to carb, etc) but it stoill would not start. Finally, he said he got some premium gas and put it in when he bought it. We dumped the premium and put in regular and it started and ran fine.

Steve

I've used 100LL avgas in all my small engines and motorcycles for many years, but just for winter storage. It doesn't go bad like car gas. Around here anyone can buy it at the local airports.

Great topic to discuss these days.

1960's Motorcycle instant tuneup with fill up at Zamperini KTOC

DJ

correction KTOA to KTOC

Ethanol is what the "borrachos" drink down here. One loudmouth gringo politico criticized Mexico's staunch anti adulterated gasoline, stand...

"We will put alcohol in our gasoline when you start putting gasoline in your Scotch"

In the midwest Casseys has no ethanol gas you can buy at some of there stores. I use it in all my small engines with sta-bil.

In the "pre ethanol" days I remember a fueler demonstrating the difference between the twist valves on his truck. The Avgas valves squeeked due to the lack of lubricity, the autogas valves were quiet. Does this have any bearing on this subject? Beats me but I thought it was interesting.

KD4UPL wrote:
Why not save your money and just buy ethanol free gas at a gas station. $5 a gallon is way to steep for me.
There are hundreds of stations in just about every state selling ethanol free for not much more money than regular. There are at least 5 of them within 20 miles of my house.

Easier said than done - for instance: in the state of California there are a total of 14 stations that sell ethanol-free gas. If you live near one of them you're good, but not everybody lives within a tankful of those stations.

If you live near a tiny Port of Entry to Mexico, none of the fuel down here is permitted to contain one single drop of ethanol. Pemex premium is 101% refined in the USA, is called Ultra Low Sulfur gasoline and is Top Tier fuel, rated among the best in the world.

Made in Mexico MAGNA however is un caballo de color diferente.