Parking up a plane. Slowing down stale fuel?

[danny_galaga]

So tomorrow might be my last flight for a while depending on how the fuel situation pans out in Australia. I'm wondering what the best thing to do is regarding the fuel tank. The tank is 94 litres. After tomorrow's flight it will have roughly 40 litres of 98 octane. I have two Jerry cans of fuel. They are a couple of months old. They are well sealed as witnessed by the plastic cans expanding and contracting with heat. The planes fuel tank is relatively sealed, but definitely not air tight like the jerry cans. The engine is a Rotax 912uls 

 

Should I:

Top up the fuel tank with the two Jerry cans.

 

Or leave it as is, relying on really fresh fuel later to dilute the (probably if some months later) slightly stale fuel. And just use my 98 to top up my car's fuel tank every second tank or so when it gets to about half? 

 

What about additives? Is there something I can get from a servo that is known to be fine with Rotax? Normally shy of additives, but am open to suggestions.

[facthunter]

 Use it in your car. Fuel can go off.  My mates Royal Enfield's fuel went off and the Fuel Pump had to be removed and dismantled. Lawn Mowers  and tractors. It's a Bacteria.. That's why you shouldn't handle Jet A1. It has something in it to prevent it happening. Nev

[danny_galaga]

Yeah, now I've written it out, I think that's the best solution. I'll try and run the tank low, it's not simple to drain. Also, on Rotax you normally just shut down via ignition, as there is no mixture control. So tomorrow I'll shut him down by turning off the fuel switch so there's virtually nothing in the carbies. I've timed how long it takes to run out of fuel. Takes 90 seconds. Longest 90 seconds I've ever sat through 😄

[skippydiesel]

In my (limited) experince;

 

98 RON is good for at least 4 weeks in the aircraft tanks (open to atmosphere)

Can be refreshed to almost origional standard by adding fresh 98 RON (shandy)

 

Why not refresh the fuel in say 4 weeks with 98 RON, fly the aircraft to 1/4-1/2 tanks - repeat every 4 weeks until normal flying start again.

 

Or drain As much 98 RON out of tanks as possible, replace with AvGas to full tank, go flying for an hour or so, park plane.

 

Depending on how long you anticipate not flying this aircraft I would:

• Drain the tanks
• Drain the fuel lines & blow out with compressed air, if in doubt as to efficacy of drain.
• Remove & drain the carburettor flat bowls
• On the last two - I doubt that running the engine until fuel exhausted will remove all of the fuel. This then leaves small amounts in system (including float bowl) which will evaporate relativly quickly, leaving a "varnish" (gluggy mess) , which may or may not cause issues when you next fuel up & try to start the engine.
• Disconnect battery & put it on trickle charge.

The 98 Ron in the "jerrycans"

• If filled to at least 75% capacity (more is better) will last at least 6 months (likly much longer), as long as container air tight.
• For container integrity - best to store out of direct sunlight

😈

[Blueadventures]

Some cars won't run well on 98, read the cars manual about fuel.  If 98 is ok use in your car.  If you need to get it used someone doing regular flying at the field may buy it off you (at the pre war price its attractive).

[BrendAn]

would it be worth refilling with avgas to keep eveything wet and prevent condensation in empty tanks.

[skippydiesel]

35 minutes ago, Blueadventures said:

Some cars won't run well on 98, read the cars manual about fuel.  If 98 is ok use in your car.  If you need to get it used someone doing regular flying at the field may buy it off you (at the pre war price its attractive).

Not sure that I agree with "Some cars won't run well on 98,..."

My understanding is that its not worth (ie nothing to be gained) putting a higher RON fuel in an engine designed to run on a lower RON. 

I recon you could put 98 RON in your your lawn mower.  It wont object , neither will  it do anything better.

Putting a lower RON in an engine designed for higher RON, will certainly not do the engine any good, may knock.

😈

[danny_galaga]

My plan if using the 98 in my car is to just top up the tank. Say half a tank. As far as I can tell, a modem car like mine will automatically adjust timing etc with the aid of different sensors like anti knock sensors.

[kgwilson]

BP produced a major study on this some years ago. 98 is generally good for up to 5 weeks in a fuel tank or if in a sealed container with little air gap about 4 months. I had some in my tank for about 7 months after the aerodrome was too wet to get out & I just added 5 litres of fresh 98 & it was fine. That is enough to refresh about 40 litres of old fuel. 98 has a number of light aromatic hydrocarbons ( Xylene, Toluene, Bezine Trymethyl benzine & others) that evaporate off first & this happens quite quickly (within 5 weeks). Interestingly the RON increases a little over that time but then often the engine is hard to start and once running it is prone to overheating which can lead to disastrous results.

 

This happened in a chainsaw that we had in the SES. It had sat for at least 6 months & someone who was not aware didn't  empty & replace the fuel with fresh as required. It was hard to start & ran till it was empty but refused to start again & there was no compression. The result was it had a hole in the piston, the big end bearing was stuffed & the bore was scored. We got a few spare parts from it though.

[Blueadventures]

17 minutes ago, danny_galaga said:

My plan if using the 98 in my car is to just top up the tank. Say half a tank. As far as I can tell, a modem car like mine will automatically adjust timing etc with the aid of different sensors like anti knock sensors.

All good but no good in an ED Ford 6cyl.

[danny_galaga]

1 hour ago, Blueadventures said:

All good but no good in an ED Ford 6cyl.

Honda Jazz, slightly more sophisticated engine ☺️

[danny_galaga]

10 hours ago, skippydiesel said:

In my (limited) experince;

 

98 RON is good for at least 4 weeks in the aircraft tanks (open to atmosphere)

Can be refreshed to almost origional standard by adding fresh 98 RON (shandy)

 

Why not refresh the fuel in say 4 weeks with 98 RON, fly the aircraft to 1/4-1/2 tanks - repeat every 4 weeks until normal flying start again.

 

Or drain As much 98 RON out of tanks as possible, replace with AvGas to full tank, go flying for an hour or so, park plane.

 

Depending on how long you anticipate not flying this aircraft I would:

• Drain the tanks
• Drain the fuel lines & blow out with compressed air, if in doubt as to efficacy of drain.
• Remove & drain the carburettor flat bowls
• On the last two - I doubt that running the engine until fuel exhausted will remove all of the fuel. This then leaves small amounts in system (including float bowl) which will evaporate relativly quickly, leaving a "varnish" (gluggy mess) , which may or may not cause issues when you next fuel up & try to start the engine.
• Disconnect battery & put it on trickle charge.

The 98 Ron in the "jerrycans"

• If filled to at least 75% capacity (more is better) will last at least 6 months (likly much longer), as long as container air tight.
• For container integrity - best to store out of direct sunlight

😈

Ok, good point on the carbies. Could actually make things worse shutting the fuel off. I will shut off normally.

 

And why not refresh the fuel in four weeks? This is the big question. How much fuel will we have? I probably use as much fuel in my car, roughly 20 litres, going to the airfield and back as in the plane. If things are tight for a while, that seems a frivolous thing to do.

 

As you say, the fuel in the cans will last a long time. They are always in a cool stable environment, so I guess I won't touch them for now. If it's ok to go to the airfield again then I can still top up the plane as I usually do

 

😇