Unleaded fuel at airfields

[440032]

The problem for us in Australia (maybe anywhere) wanting to rely on the Lycoming auto fuel approvals is that it specifies a particular specification of fuel. It doesn't just say 95 or 98 or whatever. Is the fuel we buy here to that exact specification? Doubt it/probably not. But if it was, how would you know? The dude, chick, or dude-chick/chick-dude (to be PC) at the Caltex aint going to know. As it says in the bulletin, the fuel must agree with all specifications in table 2. Lycoming has tested their engines on that exact fuel, not just any old fuel that came out of a pump at the Kwik-Fill on Lycoming Creek Road in Williamsport PA. Lycoming would never say "oh, use any old auto fuel" because they don't know and have no control over what you are getting. Their publication really says if you use this exact fuel, like we tested, you're good.

Are people using ordinary pump 95 or 98 in their LYCs here, now? You betcha.

 

I haven't looked into what say Rotax says to use - maybe they say "just use 95-98 auto fuel"

 

Jabiru says MOGAS RON 95+ if avgas is not available (and see/follow the Jabiru Service letter) That's an interesting point. If I arrived somewhere that had MOGAS and AVGAS on tap, I must choose AVGAS. Same at home base which has AVGAS avail. I should not be running MOGAS bought locally - avgas is available. I did run MOGAS for about 2 years, absolutely no difference noticed, other than black exhaust pipe with mogas, and it was a PITA to get - I didn't like transporting jerry cans in the car and stink the car out.

 

Hope this discussion has been a bit thought provoking. Do I care/mind if you use mogas? Nope! I'm not your mother.      nie mój cyrk, nie moje małpy

[Student Pilot]

I have run Lyc's, Continentals and PW engines on mogas, I dislike it intensely. It was a few years ago now, the fuel was always variable and not consistent from lots of suppliers. Hot weather made for problems, there was always a stink from the fuel. At one stage I was using 1000 litres a day and I still used avgas, I was prepared to pay more for decent fuel.

[facthunter]

Back in the 90's when some started using mogas I saw a stripped Jacobs ?/ From an ag cat and it was filthy inside All gummed up. For a motor that gets warm and is used often that was not acceptable  not just from a wear position but a safety one. A sludgy motor is likely to fail suddenly.. I've never run mogas , Just avgas and never had any issues with fuel. I also know of Rotax 912's losing compression with use of avgas and there's an explanation for that. . With mogas you need a fuel pump in the tank to ensure supply and carefully lagged fuel lines in hot areas to reduce vapour lock . Nev

 

[Kenlsa]

17 hours ago, F10 said:

I thought unleaded 100 Octane AVGAS was imminent? Seems not. It’s th one pain about a Rotax, they don’t seem to like it. Deposited of lead on the gearbox slipper clutch and I’ve seen a UTube clip about an oil change and the guy decided to clean out his oil tank. There was a lot of lead deposit sludge at the bottom of the tank. During the war, the Germans made up for their poor fuels running on as low as 87 octane as I recall, by adding to piston size. The Fw190 BMW radial, was over 40 litres in capacity. Could Lycoming/Continental drop compression and do the same? No doubt a weight and cost problem! But it would be nice to fill up on AVGAS with no worries.

My Lyc 235 @ 6.75 comp is ok to run mogas, 87 RON, with an STC that I have, so our 98 mogas is for me but I guess that anything that comes out of a bowser will work.

Ken

[kgwilson]

I've said it before but the main difference between Avgas and Petrol be it 95 or 98 RON is the composition. Avgas is based on paraffin and Petrol based on aromatic hydrocarbons. Aromatics stink and evaporate quickly. Paraffin which is the flammable component of candle wax has a light odour but they have had to add tetraethyl lead which is poisonous to it to get its anti knock (octane) rating to a high enough level to reduce the likelihood of detonation and it is less susceptible to vapor lock at reduced barometric pressure. If you use petrol and fly higher than 10,000 feet you just need a fuel pump usually electric that pushes the fuel to the engine.

 

The quality control is not a major issue if petrol is purchased from a reputable high volume retailer. I've never had a single issue with petrol that I have bought over 50 years and travelled millions of km in hundreds of vehicles. Yes I know there are examples of fuels causing engine failures but there is usually a very good explanation & a stuff up somewhere.

 

I will continue to use 98 petrol as I have since the engine was brand new. It is cleaner, cheaper, doesn't leave deposits & the oil stays relatively clean between changes. Compressions have not deteriorated & I do not add any oil between changes unlike the Avgas fanatics who always seem to be topping up.

[Ian]

The key rule is put in the engine what the manufacturer says is OK, you might take a risk based upon a risk/value assessment to vary from this however Avgas isn't magic.

There are people who believe that putting 98 Octane fuel in a car that only requires 91 is a good thing. This view isn't based on science it's based on a feeling just like people who think putting Quartz crystals by their beds protects them from cancer. If people want to spend money on bits of rock so be it. Similarly people who put more expensive blends into engines can if they want. But is may not be a view supported by science or the manufacturer.

However Leaded fuel is toxic to the point that children raised near leaded fuel outlets had significantly lower IQs than those who lived further away so it is a bad, bad thing, if you can avoid it I think you should. If you think it's good you've probably spent too much time near a bowser. (Oddly enough the guy who invented leaded fuels also invented CFCs)

Now those of you who can claim tax credits for mogas can also save another 43 or so cents per litre which is significant.

Also contrary to popular belief Australian auto fuels are standardized and conform to international norms.

 

 

 

 

 

 

[Ian]

It's what you believe. Not what's supported by science.

In an engine designed for it, each octane rating number increase will provide an efficiency dividend of approximately 1%. The key word in this sentence is designed, you need to increase the compression. My wife used to own a Subaru B4 which was designed for 100 Octane and detuned to 98 for Australia. At full boost with twin turbos in hot conditions it would ping and retard the timing so I would put some e85 to increase the RON. It was a fun car however turbos, RON and power go together. Non turbo vehicles are a different matter. 

The energy content of 91, 95 and 98 is essentially the same, E10 has a slightly lower energy content however it increases the RON. Your car is designed for 91 octane and might get a tiny increase in efficiency due to ignition advance however not on the scale that you're talking about. It is was actually true the fuel makers would be trumpeting across the airwaves as their margins are higher on 98. What you're seeing is possibly what's called a confirmation bias where you see what you want to see. A better way to test would be to get your wife to fill the car up and not tell you what fuel is being used. That being said, your car might be different from all the other cars but it's your money and if it makes you feel good do it. Personally I don't like parting with money when there's no logical reason.

Alcohol in fuel can make sense at a particular price point and if rated to do so it doesn't hurt your engine using it, in fact it has a number of benefits such as lower EGT. It's not the devil, just another fuel. Also real studies indicate that he impact on range isn't as high as the figures you believe.

This this link provides also provides a good summary. By the way the boiling temperature of Ethanol the alcohol that is used in E10 is about 78C, so boiling in the tank might be a bit of a stretch, vapour lock maybe.

Now to counter your argument I've give you a bit of maths. On average 98 is 20% more and to travel 335000km you would have put  about $50,250 of 91 fuel through it as $1.50L. If you put 98 through the engine it would have cost you $10,000. Now a RAV4 with the 6 cylinder engine with only 200,000km is being advertised on carsales for $14,000 and they might accept $10,000.

So by using the cheaper fuel you could be driving a car with 140,000 fewer km and you also get to pocket whatever you sell the car for. That's the logical and rational choice.

However we've digressed a bit from the key issue of a list of where you can get Mogas ;-)

 

[aro]

7 hours ago, Arron25 said:

Tell me how that computes with your "its all in the mind" assumptions

Cars have a knock sensor that will retard timing if detonation is detected.

If they have to retard timing from the optimum value due to low octane fuel, higher octane will give better economy.

If they can run at the optimum timing on the lower octane fuel (i.e. engine design) they get no benefit from higher octane.

 

Also, some of the 98 octane fuels claim to be "denser" i.e they need a leaner mixture.

A car with an O2 sensor will adjust the mixture and use less fuel.

If you have a mixture control in your aircraft, you might also use slightly less fuel.

A carb without manual mixture control i.e. Rotax, Jabiru will use the same amount of fuel but run slightly rich.

 

[Ian]

Quote

I have run Lyc's, Continentals and PW engines on mogas, I dislike it intensely. It was a few years ago now, the fuel was always variable and not consistent from lots of suppliers. Hot weather made for problems, there was always a stink from the fuel. At one stage I was using 1000 litres a day and I still used avgas, I was prepared to pay more for decent fuel.

It's a market, there are a number of flying schools which run mogas using very large volumes. If it works for them and is an approved fuel so be it. They keep a pretty close eye on their supply chain.

If you can afford to buy avgas and can manage the negatives both in terms of costs, health risks and deposits so be it.

[Ian]

Quote

With mogas you need a fuel pump in the tank to ensure supply and carefully lagged fuel lines in hot areas to reduce vapour lock . Nev

The testing which was conducted found that this wasn't necessarily as requirement for the Lycoming engines which were approved. Testing was conducted over a range of temperatures where fuel was heated in the tank prior to the flight.

My understanding is that the EU provided blanket approval for all planes to use mogas if the engine was approved and there hasn't been any significant impact as a result. Someone with more knowledge than me might be able to comment.

The requirement for in tank pumps relates to the engines which aren't on the approved list such as IO360 with bendix injectors. The high temperature associated with these were found to cause vapour lock.

Edited November 17, 2021 by Ian

[pmccarthy]

"We've got three grades of petrol, BP saves you money, three grades of petrol, all the power you need..." Remember the jingle?

[spacesailor]

"  put-a-tiger-in-your-tank ".

The old one.

spacesailor

[F10]

Somewhere I read from someone, some good and solid sounding advice. The trouble with Mogas, is that it isn’t subject to the quality controls AVGAS is. SOA tanker might carry a cargo of diesel, then fill up with a cargo of 95 or 98 RON, to deliver, without having to wash out the tanks. I filled upmy car with 95recently and I’m convinced it has Ethanol in it, you can smell it, smells like crushed Sugarcane. So, firstly with all the climate change zealotry out there, one would have thought we would be seeing unleaded AVGAS starting to make its appearance, or increased aviation quality controlled Mogas starting to be available at airfields, but it seems nothing yet in sight? 

[facthunter]

I think the Market for it so small that the usual way of delivering it.ie down a big overland pipe as a separate slug is not economic any more. I'm talking about the USA. Avgas WAS (by Mobil) made here as those who had serious issues with the quality of were adversely affected quite a few years ago now will no doubt recall. The fuel as delivered contained a Caustic substance which severely damaged fuel system components  Nev

[Flightrite]

That Avgas contamination in 99/00 was fortuitous for me👍

Edited November 18, 2021 by Flightrite

[kiwiaviator]

1 hour ago, facthunter said:

I think the Market for it so small that the usual way of delivering it.ie down a big overland pipe as a separate slug is not economic any more. I'm talking about the USA. Avgas WAS (by Mobil) made here as those who had serious issues with the quality of were adversely affected quite a few years ago now will no doubt recall. The fuel as delivered contained a Caustic substance which severely damaged fuel system components  Nev

Early 2000 saw this contaminated fuel ending up in New Zealand as well. I was a newly minted PPL and the C172D I was regularly flying had a fair bit of damage to the fuel components. No guarantees with any fuel however AVGAS has stricter quality controls. I am tending to use AVGAS in my J230 as a result.

[kiwiaviator]

1 minute ago, Flightrite said:

That Avgas contamination in 99/00 was fortuitous for me👍

You have piqued my interest Flightrite.. 

[Ian]

A simple test for ethanol is to get some food colouring, put it in pure petrol it should remain unmixed. If the fuel has ethanol it will colour the fuel.

To be sure test first with some e10 and pure fuel. I'd be interested if someone finds contaminated fuel.

https://backcountrypilot.org/forum/using-food-coloring-to-test-for-alcohol-in-gas-11431

Our airplanes engines are really dumb and unreliable compared to car engines however low levels of contamination shouldn't impact the RON to any significant extent, air temperature has a greater impact on RON and you don't complain about contaminated air.

Unleaded AVGAS is expensive and unlikely to appear, why would you use it if mogas is fit for purpose for 80% of the fleet?

https://generalaviationnews.com/2011/03/16/10-mogas-myths/

 

The bottom line is phase 1 is that some people will adopt avgas early and leverage the benefits they perceive and gather knowledge. Phase 2 will be those watching the first group and will adopt their practices if they don't see them falling from the sky. The Phase 3  group will never be convinced and will continue to put avgas in their tanks until it is phased out.

 

From what I'm seeing, phase 1 has occurred and we're in the middle of phase 2. Actual infrastructure is being built out and at some point will likely dominate 100LL.

 

The main driver will be price without excise mogas is currently about $1.30 L which looks pretty attractive. I thought that I read somewhere that some engines were being given an extra 1000 hours TBO when run on lead free fuels. 

 

 

 

 

[facthunter]

" I thought I read somewhere" . For heavens sake.  That won't stand up in Court. Nev

[Ian]

There an interesting video on Germany's WW2 efforts to increase power when they only had access to low octane fuel. It's good because it references NACA reports relating to specific combinations of Water/Methanol mixtures.

There's also a video on a system for current generation forced induction airplanes which can't currently use mogas. Not that I think the cost is reasonable however it does provide a significant operational safety margin.

 

[Ian]

Quote

" I thought I read somewhere" . For heavens sake.  That won't stand up in Court. Nev

I've seen opinions and stories of black gum and varnish without a skerric of a picture or other evidence but the mention of someone thinking that they read something get's a reaction. FFS 🙂

That made me laugh but anyway I didn't think that what was written here was gospel and people had a bit of a clue how to use google, so for those with the interest here's a link with the claim and another one

All in the pursuit of better practices I suppose 😉

For those who like to read, there's also a good article on Ethanol and Octane rating.

 

 

 

 

How-Does-One-Measure-Ethanol-002.pdf

Edited November 19, 2021 by Ian

[facthunter]

You left yourself open for that.  IF I've actually SEEN something  with my own eyes, it's better than having read something anywhere. Increasingly there's very questionable rubbish being published everywhere., often with vested interests.. In Aviation  you need the facts more than some  other situations.  Nev

[Ian]

All Good, it's a fair cop, the whole COVID thing is a great example of how people can grab the wrong end of the stick and refuse to believe anything that doesn't align with their point of view. I'm happy (relatively speaking) to change my mind and eat crow should the weight of evidence suggest I should do so. If there's evidence that vaccines start turning people into zombies or similar I'll reconsider my stance, but in the meantime I won't taking medical advice from Trump or Bozo on facebook. Universities, Government research organisations,  and Journals tend to be good places to get information. The thing that really makes me laugh about people with conspiracy theories involving Government is that somehow they think that the same management practices which make CASA could have some overarching secretive agenda which they've coordinated across decades; think about it. Personally I'm pleasantly surprised if a Government building has toilet paper.

I once worked on a project where one of my peers argued strongly for a significant change to a design against which I argued pretty strongly, however that evening I decided that yes he was right and spent the night changing a presentation to reflect his critique. The next day during the presentation I let people know that it was his design and tried to handball part of the presentation to him however he didn't say a word. Afterwards I asked him why and he said he was just shocked that I had changed my mind as I argued against it previously.  

[facthunter]

If you  have a good group It's best to get  the combined wisdom of it and they all feel better at being included and listened to. Later on you'll hear some claiming ownership  of things someone else did.. Like the "T" shirt. The older I get the faster I  went. . Some NEED it I suppose. The graves are full of INDISPENSIBLE People. Nev

[Ian]

One thing that I've found, especially if there's a disparity in experience between the team member is that sometimes people don't speak up when they think something is wrong/incorrect. It's a real issue for some people and cultures. Doubly so when you're flying, so in that situation always brief people, if something appears wrong or dumb speak up.