Refuelling methods for ULP

[Relfy]

Howard, that's a classic pic! I'm still laughnig. It don't git iny freesher dan dat!

 

I've heard in the motorbike circles and I think it's also in the latest jab fuels fact sheet, that when you use mogas, you shouldn't leave it in the carb and that you should run the system dry as mogas will 'gum' up the internal components over time.

 

Someone else may know why this happens?

 

 

[Guest Howard Hughes]

Howard, that's a classic pic! I'm still laughnig. It don't git iny freesher dan dat!

What I want to know is how they got there, did they just taxi up to the bowser? :thumb_up:

PS: I hope the guys at East Coast Gyros don't mind that I have linked their picture!

 

 

[Guest davidh10]

...I've heard in the motorbike circles and I think it's also in the latest jab fuels fact sheet, that when you use mogas, you shouldn't leave it in the carb and that you should run the system dry as mogas will 'gum' up the internal components over time.Someone else may know why this happens?

Would that be 2-stroke. The fuel evaporates and may leave oil residue behind. I suspect that wouldn't apply to bikes that are used frequently, but only to longer term storage.

 

I must admit I was brought up to always run the carby dry on 2-stroke mowers before storing them.

 

AFIK it does not apply to straight petrol.

 

 

[Guest davidh10]

There are several ways for fuels to go “off” however in this context I think people are concerned about octane depletion when using Mogas compared to Avgas.In very simple terms, Avgas has lower volatility and the components that give it its octane doesn’t evaporate off very easily … whereas Mogas has lighter more volatile components which evaporates more quickly thereby depleting the key octane boosting hydrocarbons in the process.

 

High quality well sealed container kept away from heat will slow the speed of octane depletion in Mogas. Unfortunately aircraft fuel tanks aren’t the ideal container … best not to store for too long in your aircraft.... fresh is best.

 

Cheers

 

Jack

Jack;

 

Would this only apply to vented containers, or those that are opened repeatedly?

 

In a sealed 20l jerry can, evaporation could only occur up to the point of vapour pressure equilibrium. On a hot day, this might be within an hour or two, while in cold weather, it would take longer. With a container of this volume, it is only going to be opened twice at most before emptying it, if it is dedicated to aircraft use. Thus I would have thought that the passage of time would not be a factor?

 

I could see the process you describe applying more to much larger, either vented, or often unsealed containers where the accumulated evaporation could be an issue. Ethanol containing fuel would be subject to the same problem at a greater rate, given the higher volatility of Ethanol and the significant contribution to RON of the Ethanol.

 

I use three 20l jerry cans dedicated to aircraft use and cycle through them, so that fuel does not get to more than about a month (or two at the most) old. I always use a Mr Funnel to pour into the aircraft, check for water and will now start checking for Ethanol, albeit that the place that I buy fuel has clear signage about which fuel contains Ethanol and a notice that it is not to be used in aircraft.

 

 

[Vev]

G’day David,

 

 

You are correct to say that limited exposure when opening containers will minimise octane depletion through evaporation and over a short period it will be very small.

 

But that’s not to say you can store fuel indefinitely, as oxidation will take place and over time will impact many of the good characteristics of fuels including octane depletion through limited exposure if stored long enough. Over the years I have seen many well sealed containers (20lt and 205lt drums) and fuel tanks fall of sludge, albeit these have been over prolonged periods and exposed to high temperature variations…. Never the less it does happen.

 

 

In terms Mogas containing of ethanol; you need to apply much the same storage considerations as any other fuels but it does tend to have heightened hydroscopic characteristic and can absorb moister from the air; thereby increasing both free and dissolved water into the fuels. This can cause problems in terms of corrosion, accelerated oxidation and burn characteristics.

 

Personally, and for what it’s worth, I’m not a fan of ethanol and go out of my way not to use it… I know other will disagree with my position on ethanol but that’s entirely my point of view.

 

 

Cheers

 

Jack

 

 

[Guest davidh10]

Thanks Jack.