How do you check alocohol content in Mogas

[Blue Albatross]

Hi everyone,

I tried to search for this question in previous posts but was unsuccessful.

Essentially, I fly my Robin on Mogas. It's about €0.20 more expensive at the pump on the airfield than it is at the petrol station next to the airfield.

However a flying colleague mentioned that I should check the alcohol levels in the fuel at the petrol station if I decide to use it. Can anyone let me know how does one go about doing this? Is it a case of looking up the info on the suppliers website, or testing the actual petrol from the pump?

Many thanks in advance
B.A.

[shortstripper]

Check this ...

http://www.lightaircraftassociation.co.uk/engineering/Mogas/OPERATING%20INFORMATION%20Iss%205.pdf

and ...

http://www.caa.co.uk/docs/33/ga_srg_09webssl04.pdf

SS :ok:

[renrut]

Try getting a glass jar that holds 100ml and put a mark on 10ml and 100ml. (I found a suitable one in my local supermarket ) Fill the jar up to 10ml with water and then top up to 100ml with Mogas. Shake and then let settle. If there in Ethanol in the fuel it will be absorbed by the water and the water level will increase. This method will give you the precentage ammount in the fuel.
I have been checking my fuel for a year now and have not found any ethanol. I always buy from a major supplier which also happens to be the cheapest

[heli1]

Can I hang an opposite question on this thread.......what about using 100LL in a high performance motor? I have nearly 150 galls which has been stored in a bowser for three years and am reluctant to use it in my aircraft until I least have got rid of enough to mix with new 50/50.So can I mix it with unleaded to use in my car and if so ,what ratio?
Advice ??.

[Jodelman]

I understand that it's illegal to use avgas in your car. Something to do with less duty being charged on avgas compared to motor fuel.

[miroc]

Pay attention, if your car has a calysator, this will be ruined very soon.

[cockney steve]

As Miroc suggests,- 100LL contains lead, this "poisons" the precious metal catalyst honeycomb in the catalytic convertor found on all UK cars after "K" registration (may be a few J-reg. fitted with a "cat")

older cars,especially Minis,Marinas and other BMC offerings in particular, had the valve-seats cut directly in the cast-iron head,-for these, lead was a necessity,to stop the seats eroding.

That apart, there's the legal aspect- no road-fuel duty paid on Avgas.

Unless the bowser has hermetic sealing (it would need to stand a considerable internal pressure on a sunny day!) the more volatile fractions of the fuel are likely to have evaporated off, therefore altering the fuels'" strength" and, on each evening cooling-cycle, moist atmospheric air would be drawn through the vent and condense in the tank....always top up your fuel before storing your car/boat/plane :)

If it's the usual low-revving, long-stroke,conservatively-rated Aviation engine in your Robin, all the forgoing is probably purely academic.

I'd check the bowser for water content,give it a good mixing (yes! there's a possibility it's stratified-"separated out" and then do a ground-run on a gallon. If the engine performed satisfactorily, i'd feel OK to use it........but it's your cash, your plane and your life! :}

Edit at7.50....If I paid more attention, I'd NOT have aimed this at the OP. but the same caveats still apply and old, stale 100LL would , IMHO, NOT perform well in an older, high compression road-engine, but may be OK in the side-valve Fords and iron -head BMC's , wooly low-compression Landrovers etc.

[renrut]

Is this an aeroplane site or somewhere where Geeks can expound on their knowledge os other subjects:=

[Rod1]

Ethanol in Mogas is very defiantly a subject which is important to aircraft operators. Almost all the aircraft at my strip operate on Mogas.

Rod1

[Mariner9]

Continuing in Geek :8 mode, and firstly in response to the 3yr old Avgas, the main problem will most likely be the formation of gums. The high Octane rating in Avgas is achieved primarily by relatively low vapour pressure components such as toluene (and the lead!), so octane drop through evaporation is less likely (though not impossible). You could always get a sample tested, but a full spec Avgas test costs >£1000 :ouch:

Second, with regard to alcohol, the prescribed test mentioned above should be undertaken. If there is no measurable increase in the water level use the fuel. This does not mean the fuel is free from alcohol, but that iit has satisfactorily passed the test and therefore deemed "safe" for use by our Lords & Masters at the CAA.

Out of interest, virtually no mogas in the UK is completely alcohol free nowadays due to the integrated supply chain here. Of interest to any Jet jockeys that may occasionally view this lowly forum is that this is also the case for Jet A-1. Indeed, the industry is hurriedly developing testing methodology and establishing sensible limits for the allowable quantity of FAME (biodiesel) in Jet A-1 :8 Sadly, and probably due to the lack of any serious commercial pressures, they don't appear to be taking a similar pragmatic approach to Mogas :ugh:

[worrab]

Maybe you could breathalyse it?

(Sorry - couldn't resist)

[hum]

YouTube - ethanol vid.wmv (http://www.youtube.com/watch?v=1O5sBrq4MJM)

[Romeo Tango]

I find that avgas kept in my bowser for over a year or so works ok in my Robin (O-360) but does not make as many horsepower as brand new stuff.

[S-Works]

Avgas is designed to be stored for many years and gumming etc is not a real issue. 3 year old Avgas is not going to have changed in any meaningful manner.

I use it on my off road XT600 mixed with a bit of Mogas. Lovely!! :p

[rans6andrew]

If water absorbs the ethanol from the fuel, why do we not just add water to the fuel, let it absorb the ethanol, let it settle and then decant off the ethanol free portion?

My Mr Funnel separates the water from fuel reliably. Just need to know how much water is needed, as a percentage, to take out 10% ethanol by volume.

Anyone?

[Pilot DAR]

but does not make as many horsepower as brand new stuff.

Hmmm, I'm not sure how you'd measure this, other than a dynamometer check of the engine. Be assured that aged Avgas, will be operationally identical to fresh Avgas, as long as there is no contamination.

Now, contamination...

Let's step back to the beginning: No matter what engine your aircraft has, there will be a specified fuel(s) for use in that engine. That fuel specification will describe the properties of the fuel in many terms, all of which are "testable". Water and alcohols are a part of this specificaton. The specification also states an energy content requirement, which equates roughly to power output. It is the pilot's responsibility to operate the aircraft using fuel which meets the specification. Generally, we pilots just accept that the fuel we are buying does meet the spec, though if in doubt, you are entitled to ask for certification. (when you sample your sumps for water, its not because you think you bought fuul with water in it, but because it is likely that your fuel system condensed the water into the fuel).

Therefore, knowing that there is a spec, and that you are required to conform to it, it stands to reason, that taking the fuel off spec yourself is a bad idea.

Therefore; why do we not just add water to the fuel, let it absorb the ethanol, let it settle and then decant off the ethanol free portion? is a no-no. I won't get into why the chemistry of doing this just will not work, it just won't. We don't want water or ethanol in our fuel, so adding either is a poor idea.

Operated properly, and with appropriate design changes, ethanol works in many planes. We flew a C 150 on pure ethanol for two years experimentally, and never had a problem. (other than arriving smelling like a distillery!). a number of other aircraft have been similarly operated on test programs, However, mixtures of gasoline and ethanol which are not approved in the aircraft, are not to be used for a number of safety reasons.

For those who really want to delve into this subject, I recommend the book: "Future Fuels for General Aviation" by Struass and Gonzalez, ISBN 0-8031-1263-7.

[Barry Plumb]

Gents,
Please do not be tempted to wash the ethanol out of Mogas as suggested here. Mogas to EN228 has an octane rating of 95 RON. Removing the ethanol from the fuel (presently most fuel contains 5% ethanol) will reduce the octane rating by two to three points. This would probably be enough to make a Rotax or other fairly high compression engines run into detonation at full power.
Quite appart from the dangerous and messy operation of washing the fuel, you will also need to think of how to dospose of the residue.

On the subject of testing fuel for alcohol the water test method is very inaccurate at low concentrations, since the increase in volume in the water results in very little movement of the meniscus.

There are very sensitive colour change test kits that are readily available from Airworld UK Ltd at reasonable cost. The kits are called Bluebud and Bluebottle test kits. These will give a litmus type colour change if the test fuel contains more than approx 1% alcohol. Type the word Blue into the search tool on the Airworld UK website.

Happy Landings
Barry Plumb

[liam548]

is it not the same method as checking for alcohol in avgas?

[Rod1]

“There are very sensitive colour change test kits that are readily available from Airworld UK Ltd at reasonable cost. The kits are called Bluebud and Bluebottle test kits. These will give a litmus type colour change if the test fuel contains more than approx 1% alcohol. Type the word Blue into the search tool on the Airworld UK website.”

The Avgas spec allows 2% alcohol…

Rod1