Avgas vs Autogas

[dewhitaker]

Re: Avgas vs Autogas

The pictures you can see here show what a steady diet of 100LL will do to a small engine after only 300 hours. As Mike stated, there is too much carbon build up using 100LL. This problem was discovered last year on our airplane. It started with a stuck valve. My dad insisted we pull a cylinder and take a look, it was not acceptable to him to just free up the valve and keep flying. Boy am I glad I listened to Dad!

Of the 4 jugs, two had stuck piston rings. You can clearly see the carbon was chipping off the pistons and scoring them. Finding this, we went further and removed the oil tank and found the carbon chips had migrated to the oil pick up screen and it was probably 30% blocked.

Keep in mind this engine had only 300 hours on it from its last top overhaul. Needless to say it got another one last year. My advice to anyone is get the mogas STC and blend 1 gallon of 100LL and 4 gallons of unleaded together and if you feel like it, 2 ounces of MMO. This will give you the correct lead content for these little engines. Also, please be inquisitive: IF you have a stuck valve, it may be tempting to just get it unstuck and keep flying, but please reconsider, there may be more going on inside your engine than you think.

[flylo]

Re: Avgas vs Autogas

"My advice to anyone is get the mogas STC and blend 1 gallon of 100LL and 4 gallons of unleaded together and if you feel like it, 2 ounces of MMO."

This is the mix I use & it works well for me. Eric

[flyguy]

Re: Avgas vs Autogas

Thanks for the pix and info. My overhaul has about 300 hours on it and the top of the pistons are developing a lead/carbon coating similar to your pictures.
If I am not mistaken an analysis of the nasty looking pinkish stuff, not sure about the white, is lead (probably oxide) not carbon. Needless to say there is quite a a bit of carbon mixed in.
I think that you will also find that the little chips in the oil screen that look like pinkish cat sand are also lead (oxide.) Appears from some tests that I ran that the oxide is really abrasive.

There is no auto gas available here that doesn't have ethanol in it, but I am begining to wish that I had not worried about the 5% ethanol, the seals, the hoses and the aluminum tanks about 200 hours ago and just saved my engine.

Sure glad I don't have a $30,000 Lycoming big bore up front.
DC

[Pearson]

Re: Avgas vs Autogas

Is there a cost effective way to remove alcohol from auto gas?

[Hank Jarrett]

Re: Avgas vs Autogas

Our little A-65 will run on 73 octane, that's the reqiurement in the type certificate last I looked.

Hard to imagine that a bit of ethanol will drag 87 octane done to less than 73.

Mine has run great on mogas for 15 years or more, BUT gas with ethanol is excluded from my stc and I don't use it.

I think it has more to do with alcohol being a solvent for the sloshing compunds than anything else.

Dave

Just a quick clarification in case my past post was confusing. Alcohol INCREASES the octane number of gasoline. Higher octane readings mean the fuel flame front moves SLOWER during combustion and reduced detonation. That's why you need it for higher compression engines. There is actually LESS energy in high octane fuel than low Acton, but the higher compression ratios allows even more fuel and air to be packed in giving the higher overall power (with WAY higher fuel consumption per horsepower).
The problem with alcohol in the fuel isn't that it lowers the octane level, it is the damage the alcohol does in the airplane.
Hank

[KewFlyer]

Re: Avgas vs Autogas

Somo info picked up over the week end:
For those of you that have CITCO gas stations, as we do here in Virginia, CITCO appears to be one of the few mogas suppliers NOT adding ethanol....so far...at least here in northern VA. Someone from the EAA chapter also mentioned VALERO (?) as another non ethanol mogas source.
My 2 cents

[crispy critter]

Re: Avgas vs Autogas

Thanks for the pix and info. My overhaul has about 300 hours on it and the top of the pistons are developing a lead/carbon coating similar to your pictures.
If I am not mistaken an analysis of the nasty looking pinkish stuff, not sure about the white, is lead (probably oxide) not carbon. Needless to say there is quite a a bit of carbon mixed in.
I think that you will also find that the little chips in the oil screen that look like pinkish cat sand are also lead (oxide.) Appears from some tests that I ran that the oxide is really abrasive.

There is no auto gas available here that doesn't have ethanol in it, but I am begining to wish that I had not worried about the 5% ethanol, the seals, the hoses and the aluminum tanks about 200 hours ago and just saved my engine.

Sure glad I don't have a $30,000 Lycoming big bore up front.
DC

Flyguy,
Find where your nearest fuel distributer is(bulk plant)....you will find alcohol free gas there.

[M Towsley]

Re: Avgas vs Autogas

Guys,

As I have posted in the past, try testing the high grade from one of the majors, Shell, BP, Exxon/Mobil, etc. They usually don't use ethanol in the higher grades. Test to be positive, though. Who knows what they do in California with all of their emission laws. Good luck DC and hopefully you can test the higher grade fuels.

Regarding Citgo and Valero. Remember, ALL of the fuel companies buy and sell from each other, both in the pipeline and in the fuel truck. All 87 grade is the same. It is the higher grades where the majors mix their special blend as the truck is pulling out of the terminal. Not to say you can't get ethanol free, as I was able to do so here in the 87 grade. Just don't trust what the pump or station owner says, test it!

[Jim Herpst]

Re: Avgas vs Autogas

Guys, As always the truth comes to light. I was told from my engine re-builder to use 100 LL for the first 25 hours in The a-65 in the Baby Ace. I am doing that...he probably wants the valve seats to get some lead for break in BUT I am going to go to Auot gas /100LL 4 to 1 mix after I get 13 more hours on her. I dont like the Alc in it. I will investigate the bulk supplier and see if we can get a tank nearby. Great discussion (AND PICS!!)

JIM

[crispy critter]

Re: Avgas vs Autogas

I always use a 50/50 blend for the first 2-4 hours of a break-in and sometimes(espesially with a lycoming)100% 100LL. After that I go to what ever I plan on getting her used to running on.

[dewhitaker]

Re: Avgas vs Autogas

Hi everyone, yes we buy our fuel from the local BP Oil in 300 gallon quantity, and I test it for presence of alcohol at delivery. They are quite happy to provide alcohol free gasoline for our off road use for the tractor to mow 12 acres. It takes us about 600 to 900 gallons of gasoline each mowing season.

Here is a position paper from the EAA on this growing problem, it makes for interesting reading.

[VictorBravo]

Re: Avgas vs Autogas

Is there a cost effective way to remove alcohol from auto gas?

A Chemist friend of mine and I are working on it now.... stay tuned.

[CJ Ross]

Re: Avgas vs Autogas

I ran 87 auto gas in my 65 95% for over 16 years. Probably had 900hrs when I sold it and never had a problem. The stromburg carb was a bit tempermental sometimes but thats the nature of it. I have talked to a friend that drives the gas tanker here and have a list of places that do not have ethanol as I'm not a big fan of that either. I try not to run it in the truck much less the plane. Just my opinion

[N96337]

Re: Avgas vs Autogas

Guys,

All 87 grade is the same. It is the higher grades where the majors mix their special blend as the truck is pulling out of the terminal. Not to say you can't get ethanol free, as I was able to do so here in the 87 grade. Just don't trust what the pump or station owner says, test it!

Marty, when I used to haul fuel, there was (and I presume still is) a "2 point" margin on octane.... one station we fueled daily sold 87, 89, & 91 octane fuel (at corespondinly different prices)... yet we only hauled ONE product to them... yep, 89 octane..10% blend with alcohol. Also, more than once, we would dump a few hundred gallons of higher octane in the unlead tanks to keep them from running out before we got back with the proper grade fuel (we had more than one station that could easily run through 25,000 gallons each day).This isn't uncommon, and it's totally legal, so the important thing to do is TEST!!!!

John

[Gary Snell]

Re: Avgas vs Autogas

I'm done with 100LL in the small continentals except on breakin. Had an exhaust valve hang open on takeoff last weekend and had a close encounter with the neighbors trees. This was on a 140 with a C90 that has been on a steady diet of 100LL from a previous owner. Buildup on the valve stem/guide from the 100LL was definitely the cause.