AvGas or Unleaded?

[kgwilson]

I was called out at 1:00am on Saturday morning as a 6 kVA generator we (SES) had loaned to the Glenreagh RFS wouldn't start & they had evacuees from the fires coming to the hall & they thought the power was about to go. First I checked the spark with another plug. All good, then the fuel filter, all good. Removed the plug & it was wet but no smell of petrol, removed the carb float bowl & emptied the water out. Turned on the fuel tap & flushed the line, reconnected everything & it started first pull. Hondas always start. The fuel was stale about a year old but 91 octane so not too bad. The tank was half full. The Generator had been stored in the shed & not run since we loaned it to them a year ago. The water had come from condensation over the year of heating and cooling cycles with humid air cycling through the breather over that time. A tiny drop each time accumulated enough to fill the carb float bowl. I gave them a lecture on Generator maintenance (run a minimum of once a month with a load) & went home to bed.

 

The fuel tanks on my aircraft are vinylester & in theory I should not get condensation but I found a tiny amount in the fuel tester once after not flying over a period of high diurnal temperature change days. Water can be a problem anywhere.

 

 

[facthunter]

 The material it's made from makes little difference as it's the temp of the fuel and vapour above it, where the moisture is,  that matters. Reducing the airspace was once widely practiced.  Ie the tanks were filled to the brim before putting the plane in the hangar. These days that generally doesn't happen, for some good reasons. Ideally. a plane will operate every day when this problem  won't be an issue. unless the fuel itself is the source/problem. Nev

 

 

[onetrack]

Have a mate that filled up his diesel ute 3 hours west of Perth while a tanker was doing a delivery

 

Butch, I think you have your compass points screwed up. There's nothing but many sq kms of ocean, 3 hrs West of Perth. I presume you meant to write, East of Perth.

 

The common rail fuel injection systems on the current diesels need very clean fuel, because injector and high pressure pump tolerances are now half what they used to be - around 0.0005" (0.0127mm), and the pressures are huge (25,000psi to 30,000psi/172 to 206mPa). Any water in these components reduces the lubrication between them, and therefore fuel system damage is guaranteed.

 

Sizeable amounts of water in fuel should not get through filters, the filter should simply block up, and the engine should starve of fuel. The utes filtering system is obviously poor, if the fuel pump can suck water through it. There's a booming market selling "add-on", high quality fuel filtering systems to the 4WD diesel crowd, to prevent engine damage from fuel contamination.

 

 

[skippydiesel]

 

 

 

Butch, I think you have your compass points screwed up. There's nothing but many sq kms of ocean, 3 hrs West of Perth. I presume you meant to write, East of Perth.

 

No he's  right on the ball - a lot of water in his fuel or is it a little fuel in his water - I get confused!

 

On another note: I too have had dodgy fuel - many many years ago filled up (with diesel) at a no name el cheapo servo - got a tank full of something not quite diesel. Engine didn't stop but power so low that, on hill near our place that I would go up in 5th, down to 2nd with lots of smoke. Drained tank refilled and the car "came good" !

 

I have never used no name servos since and as I said had no problems at all.

 

 

[Butch]

Butch, I think you have your compass points screwed up. There's nothing but many sq kms of ocean, 3 hrs West of Perth. I presume you meant to write, East of Perth.

 

The common rail fuel injection systems on the current diesels need very clean fuel, because injector and high pressure pump tolerances are now half what they used to be - around 0.0005" (0.0127mm), and the pressures are huge (25,000psi to 30,000psi/172 to 206mPa). Any water in these components reduces the lubrication between them, and therefore fuel system damage is guaranteed.

 

Sizeable amounts of water in fuel should not get through filters, the filter should simply block up, and the engine should starve of fuel. The utes filtering system is obviously poor, if the fuel pump can suck water through it. There's a booming market selling "add-on", high quality fuel filtering systems to the 4WD diesel crowd, to prevent engine damage from fuel contamination

 

Yep Skippy meant East! ( failed my nav test lol  )

 

Just brought a new Triton ute, rang the service department of my local dealer and inquired which side of the original filter should I fit an after market water trap and filter in the fuel line ?

 

 Stern reply was if you fit any type of after market filters you could void your warranty, as far as they are concerned there are adequate filters and it could interfere with the water contamination warning sensor.

 

My mates ute was a Mazda BT50 and there's a bitch fight between the servo, fuel company, insurance and Mazda about who takes the blame and pays the bills.  

 

 

[skippydiesel]

Hi Butch - The debate over additional fuel filtration on small diesels is almost as long as they have been around.

 

These days the emphasis seems to be having the same micron filter as the OM WITH an additional nice big water separator and water warning system.

 

I think the idea is that the filter(s) are more than good enough for removing solids but the OM system does not have enough capacity/early warning to stop you in time from trashing the common rail.

 

Most conversations, I have followed, have the additional filter/water separator befor/upstream of the OM system but I guess that's up to the installer. Certainly there is little point in having a larger micron filter downstream and one needs to be careful that a smaller micron is not interfering with fuel delivery.

 

 

[facthunter]

Getting back to planes,... the Rotax 912 s were recommended for mogas, as they don't react well to lead  as it doesn't get hot enough in their heads to activate it's function properly and the build up on the seats can  have a partial "lift off" causing compression loss and possible valve and /or seat damage. I've actually seen this happen and fortunately reverting to mogas rectified it in a short time, but not surew if that can always be guaranteed. LL100 is a certified product whereas Mogas is open to tampering/contamination (as is an opened LL100 container.) I've also seen some stripped Radials out of a Grumman AG CAT that showed a lot of gumming on mogas , but that's quite a while ago now. I've NEVER operated a Lycoming or Continental with Mogas even though some of them are supposedly OK for it. Apart from anything else the aero oils are made for it (the lead) although there has been some concern for some aviation fuels used in the NT, lately, detonating and having premature failures which I think CASA got involved with about a year ago. Nev

 

 

[Bruce Tuncks]

I have read that there is a chance of wrecking your engine if you put in contaminated fuel. This was in a discussion on insurance. Apparently Youi will not pay out for the repairs but some other companies do.

 

Since reading this, I have been looking at Youi ads to see if this is mentioned, but I only see lovely young women smiling while helping their customers.

 

I never knew that better filtration could stop contaminated fuel from causing a problem, so thanks guys.

 

 

[Bruce Tuncks]

I should have said motor cars...  The Jabiru uses avgas because this is in the bowser. I have never seen or heard of anything wrong with it.

 

More expensive and a dirtier engine , but probably the safest option I reckon.

 

 

[facthunter]

Why would it be a dirtier engine  with LL100. especially if you use the aero oils that are recommended by Jabiru and get the temps to where they should be oil wise.? 85 -90 degrees C. Nev

 

 

[skippydiesel]

Why would it be a dirtier engine  with LL100. especially if you use the aero oils that are recommended by Jabiru and get the temps to where they should be oil wise.? 85 -90 degrees C. Nev

 

Lead!

 

It seems to me that if the engine is designed for ULP, then it runs just fine on the stuff, putting AvGas in serves no beneficial purpose, other than to lighten your wallet & stroke your perceptions.

 

On the other hand if its designed for AvGas and you use ULP without modifications (even with an STC) then problems may ensue.

 

 

[facthunter]

The preferred Jabiru fuel was  100LL . They might have relaxed that out of need to embrace what's out there later in the game...

 

    100% of all the planes I've flown (Pistons) (excluding 912's and two strokes and GYPSY Majors with bronze heads) have used 100 or higher octane Leaded fuels and I've raced cars on 100LL. NEVER a trace of lead deposits and only sometimes a problem with spark plugs.( Maybe 3 times in 50+years in aircraft)  AERO oils are designed for 100LL and you can get them both at most aerodromes .The only "dirt" (gum) I've seen in aero engines was when they ran on MOGAS I have no desire to use it. and that was the advice of every engine shop I knew of, so why risk it. Nothing to do with stroking my perceptions ,whatever that means. MOGAS is not a  quality controlled product, especially in this country where some states mandate ethanol  and people can add what they choose to the mix IF no ones looking. Nev

 

 

[kgwilson]

The difference when taking a head off a Jab engine running Avgas & one using 98 ULP is very noticeable. The Avgas heads & cylinder tops generally have deposits on them & the 98 ULP heads & cylinder tops don't. Avgas also fouls plugs especially running full rich and the engine is not hot. Jabiru recommend Avgas but also advise Mogas 95 or higher is OK. The only reason I can think of for the recommendation is quality control and the possibility of vapour locks with Mogas

 

 

[facthunter]

 A lot of that deposit depends on oil use, mixture and dust and the amount of idling/taxying. I've run  lot of older bikes etc on avgas when it was allowed. and the motors ran much cleaner with less oil dilution.. You will recall the white pipes which were a tell tale of the fact you were running 100LL and the mixture was spot on.. Most race cars in the 60's ran avgas to get the octane rating. The white pipe was due to the bromine that got rid of the lead and the oil stayed much less darkened than with mogas. (but that also is a function of mixture and thorough burning) .There's some rubbish aromatics and bad stuff in Mogas. Nev

 

 

[skippydiesel]

The preferred Jabiru fuel was  100LL . They might have relaxed that out of need to embrace what's out there later in the game...

 

    100% of all the planes I've flown (Pistons) (excluding 912's and two strokes and GYPSY Majors with bronze heads) have used 100 or higher octane Leaded fuels and I've raced cars on 100LL. NEVER a trace of lead deposits and only sometimes a problem with spark plugs.( Maybe 3 times in 50+years in aircraft)  AERO oils are designed for 100LL and you can get them both at most aerodromes .The only "dirt" (gum) I've seen in aero engines was when they ran on MOGAS I have no desire to use it. and that was the advice of every engine shop I knew of, so why risk it. Nothing to do with stroking my perceptions ,whatever that means. MOGAS is not a  quality controlled product, especially in this country where some states mandate ethanol  and people can add what they choose to the mix IF no ones looking. Nev

 

Nev Nnev - lead is a pollutant in our atmosphere, does terrible things to the neural system/brain - especially in children. Why - Oh - why would you be an advocate ?

 

ULP/PULP/MOGAS whatever, runs our cars and has done since about 1985 or so - it seem to be perfectly acceptable to Rotax 912/914's - no more risk than aviating itself. In fact AvGas is decidedly non beneficial to the Rotax - as I pointed out , why put AvGas into an engine that will not benefit from it/will only cause it harm - it can only be perversity or some other ego driven urge, it's  certainly not logical. 

 

No offence Nev but the numbers are against you - most 912/914's run on unleaded and have done so for many thousands (if not millions by now) of hours with very few fuel related issues (probably less than AvGas and its potential to cause deposits - not every pilot has your skill /knowledge with engine management).

 

It would seem you are unaware, all recent Rotax 912/914's are certified to run up to 10% ethanol/ULP - no problem (can't say I would want to but that's another debate) conditional on fuel storage & delivery systems also being compatible with ethanol.

 

As for engines designed for AvGas - I agree with you - use AvGas!. Anything else has the potential to have a harmful (engine) outcome. 

 

Hopefully your bogeyman statement about "people can add what they choose to the mix" is largely a thing of the past and certainly not practised by the mainstream fuel companies.

 

 

[pmccarthy]

My Lycoming O360 runs on a blend of mogas and avgas, mix varies from week to week. Sometimes, but not often, pure mogas. Has an STC and doesn’t seem to cause any problems. 

 

 

[skippydiesel]

My Lycoming O360 runs on a blend of mogas and avgas, mix varies from week to week. Sometimes, but not often, pure mogas. Has an STC and doesn’t seem to cause any problems. 

 

Good oh! - I have no experience of STC'd engines so should probably not comment, but I just cant help myself;  I am of the generation that saw the move from leaded fuels to unleaded. Having also lived in Europe for many years, I was familiar with high octane petrol for high compression engines - mainly sport cars and lower octanes for lesser engines (dont think Au had as much choice, certainly outside the major cities). We were always counseled against using lower octane fuels in high compression engines (cause "knocking" etc). Conversely using these fuels in lower compression engines might make us feel good but did nothing for the engine, just lightened the wallet for no gain.

 

Whats all this got to do with aircraft engines?

 

Perhaps nothing but the lessons learnt back then are still with me and the thought of using a fuel that the engine was not specifically designed/constructed for goes very much "against the grain" - I do appreciate that modifications can be made to adapt an engine and may be your Lycoming was designed from the outset to run on both but it still makes me uneasy.

 

I am with Nev on the use of the correct fuel for the engine.

 

 

[jetjr]

Additions to ULP is common practice and not illegal (I don't think) unless it undermines base specs. Each company has its own additive pack in addition to rinsing and stirring of tanks.

 

A major difference between aviation and road users is ULP is now largely running through EFI engines that can easily handle such changes in SG and via ECU, control mixtures to prevent engine damage. Except a very few aircraft this is not the case in aviation. A 10% increase in fuel burn or decrease in performance wouldn't be noticed by many road users.

 

As per document I added last post you will see the SG change and subsequent mixture change after just a few weeks from refinery

 

Id have thought the age of fuel at a std regional servo would be well into this time window.

 

If ULP isn't used quickly you can damage the engine.

 

If its jetted and setup for it probably no issues. Ethanol can harm more than just the engine, Rotax may be OK but aircraft fuel system may not be up to it.

 

The volume of fuel used for piston aviation fleet is miniscule so no the lead shouldn't concern many.

 

Did anyone notice several brands in NSW have ethanol in their 95 now?

 

 

[kgwilson]

I changed to 98 when BP began adding ethanol to their 95 over a year ago.

 

 

[facthunter]

While "some" engines may be OK with ethanol blends it's somewhat risky if it's using a conventional carburetter without making a mixture adjustment in which case you would need to know exactly what % of ethanol is actually in the formulation. and adjust for it.. Trouble is MOGAS is many things which are not controlled (whether you hope it is or not).. One day ethanol may be THE fuel we use and that can be coped with as it is on some ops in Brazil. Then we would have fuel system materials and oils etc specifically for it. E 85 is a majority ethanol fuel and if you want to use that in the right motor it would /could be quite safe (but you would use a lot more and it's not yet widely available.)

 

    Incidently I've NEVER ever advised an operator of a 912 or the other engines I mentioned to run AVGAS and in the case of the 912 gave precise reasons why it's not a particularly good idea.

 

   I'm also glad that lead is not in auto fuels especially those that are used in cities. but the 2 most dangerously polluted places in Australia for lead are Mt ISA and Broken Hill and vehicles didn't cause that, but cars can ALSO just pull to the side of the road when the engines expire so that makes an aero engine a bit special.. Nev

 

 

[skippydiesel]

The old saying "the proof of the pudding, is in the eating" -in the Rotax /ULP debate, I think that with so many units in operation, around the world, without drama (related to fuel) all the wise counsel regarding fuel QA , adulteration,  aging, etc is good as cautionary advice , rather than any on going problem.

 

The climate change debate is bogged down by countries claiming to contribute little to the problem or demanding more time to develop/pollute. Lead is much the same story, just because aircraft contribute very little is no reason not to try and phase it out  ( yes I know that there is no viable alternative  - yet!) 

 

 

[Bruce Tuncks]

I reckon I saw in Supercheap a can of stuff which said in the label it was lead replacement.

 

Sooner or later we won't be able to buy avgas, probably because of the market size. 

 

What does the lead actually do? It increases the octane rating and helps lubricate the upper cylinder I think but don't know how.

 

So why is there no replacement already?

 

 

[kgwilson]

2008 and later Lycoming 0360 & i0360 engines are OK to run on Mogas but Lycoming put a number of of conditions on this including the lack of quality control over Mogas products so they do not make any specific recommendations. Jabiru advise that Mogas is a recommended fuel with some conditions. Extract from the manual below..

 

3.7 Fuel

 

3.7.1 Recommended Fuel Types:

 

Table 4 – Fuel Types

 

Fuel:

 

2200 Applicability

 

3300 Applicability

 

- AVGAS 100LL & AVGAS 100/130

 

All S/No.

 

All S/No.

 

- Leaded & Unleaded Automotive Gasoline above 95 Octane RON (AKI 90)

 

S/No. 22B001 on

 

S/No. 22C001 on

 

S/No. 33A224 on

 

S/No. 33L001 on

 

Notes:

 

1. Table 4 provides basic information only. Detailed information is available in Jabiru Service Letter JSL007.

 

2. Due to poor control of quality and content Automotive Gasoline (MOGAS) is used at the operator’s risk. JSL007 refers.

 

WARNING

 

It is important to realise that due to the lower QA standards, even following best practice it is still possible for a particular tank-full of MOGAS to be unsuitable or unsafe for use in a Jabiru Engine. Jabiru Aircraft may choose to void any warranty for engines which have been damaged due to “bad” MOGAS. Operators use MOGAS at their own risk.

 

 

[kgwilson]

 

What does the lead actually do? It increases the octane rating and helps lubricate the upper cylinder I think but don't know how.

 

It is explained quite well in the Jabiru Fuel Guidance service bulletin. Copy attached

 

JSL007-7_Fuel_Guidance.pdf

 

 

[facthunter]

There's a brief reference to "valve GUIDES" etc in a couple of lines. My understanding is that the engine parts "helped" must get to  a sufficiently high temp to make the TEL Melt like a flux does when brazing and that only the exhaust valve seat would benefit. These days valve and seat material is good enough to not require TEL and allow engines tor run on things like LPG and lead free Mogas . Bronze valve seats (or heads) will last no time with TEL in the fuel as the lead compound alloys with the seat metal. I mentioned Bromine (compounds) being used to remove/limit the TEL deposits. Since there's no mention of that in any of that material maybe it's discontinued. No more white inside the exhaust pipes.

 

   Some of those compression ratios are quite high and could make engines operation much more critical. IF you operate at an aerodrome a few thousand feet up all is well. It's a wonder more reference is not made to spark plug heat range and a loose or not properly tightened plug will overheat.

 

  That's a pretty comprehensive coverage of the matter, that should have a few of you worried.. All is not well in the fuel world, for aeroplanes.  Nev