Premium Mogas

[biggles5128]

Was just reading notes from Jabiru engineer in respect to a chemical called Toluene which is found in some automotive fuels. Apparently this substance reacts with the sealant in the Jabiru fuel tanks. A particular brand of fuel was named as a common factor (I won't name it but you can look it up on their site).

 

I have started using Caltex Vortex 98 and have not seen any issues. Has any other operator experienced problems with the fuel tanks and if so what fuel has been used?

 

Can anyone in the petroleum industry enlighten us to prevalence of this substance?

 

 

[Keenaviator]

Apparently Jabiru are recommending that if we use mogas, stick with 95 which doesn't have as much of the aromatics which are believed to be responsible to damaging Jabiru fuel tanks. I've just sloshed my with 'Creme' which is supposed to be resistant to even ethanol blends, not that I will be testing it knowingly.

 

Laurie

 

 

[metalman]

I've been using either BP 98 or shell , no problems with the fuel or the tanks, but it's made a hell ova mess of my lexan windows.

 

What resin are jabiru using?

 

 

[Keenaviator]

I've been using either BP 98 or shell , no problems with the fuel or the tanks, but it's made a hell ova mess of my lexan windows.What resin are jabiru using?

Probably the stuff they build the aircraft with, an aroldite product.

 

Some time ago I did some tests strips of glass with 'bote cote' the resin soaking in jars of mogas and avgas for well over 12 months. The glass reinforced with 'bote cote' appeared to be unaffected. I used it to secure the fuel cap insert in my Starlet fuel tank and it is still going strong.

 

Laurie

 

 

[Guest Andys@coffs]

Keith Rule in Cessnock NSW was talking to me about exactly this problem in his Jabby and his Header tank.....Give him a ring and discuss....I recall from him that the fix is painful and not assured.....He switched back to Avgas....I seem to remember him saying a new header tank was >$500 bucks from J

 

Andy

 

 

[biggles5128]

Would it be a case of use once and you will have a problem or would it be a build up effect

 

 

[Old Koreelah]

What resin are jabiru using?

I have been told they use Epoxy resin, and Australian-made E glass.

 

 

[deadstick]

I have run Caltex 98 for a long time, no tank problems thus far.

 

 

[Oscar]

People need to be aware that fuels may not always be exactly what appears on the label! A friend of mine used to be the manager at the Shell refinery at Clyde, and told me one day a funny story about a new young apprentice worker who told him that the premium fuel Shell was providing was not as good as the premium fuel from BP - next door - how his car ran better on BP etc. My friend patted him on the shoulder and said: 'well you'd better just go on using BP, then' - because he knew that the fuel that left BP's facility on their trucks for delivery to the Service Stations had arrived in the BP facility from two pipes going there from the Shell refinery! BP was for that area nothing more than a Shell re-seller!

 

Dafydd Llewellyn's letter detailing the problems with Mogas in the Feb. 2013 issue of Sport Pilot provides a great deal of information that users of Mogas should know.

 

 

[biggles5128]

I know the suggestion was to use 95 octane instead of 98, my concern would be that it would lose potency while sitting in the tanks after a week or two whereby 98 gives a little better margin.

 

 

[AVOCET]

I have been told they use Epoxy resin, and Australian-made E glass.

Hi , they make the fuel tanks and every thing else from epoxy LC 3600 resin and ARADURE

 

hardener , 3:1 ratio .

 

You can get it from jabiru in 4 ltr plastic bottles , or MURIE enterprises iin Sydney or Melbourne ,

 

In small quantities its cheeper to get it from jabiru

 

Cheers

 

 

[cscotthendry]

I read somwhere that Shell did have problems with their earlier blends of premium unleaded eating out fuel pumps and seals but that they subsequently changed their forumlations to rectify that. I believe that this goes way back to the eighties.

 

 

[Gnarly Gnu]

Can anyone in the petroleum industry enlighten us to prevalence of this substance?

Not in the petroleum industry but used to add some toluene to petrol as an octane booster, it's a fairly common solvent used in coatings etc - probably why some coatings aren't going to like it.... worked OK in my old Ford.

 

 

[BoxFat]

The comment by Biggles about potential loss of potency (anti-knock rating ?) during storage has started me thinking. There are undoubtedly a wide range of professions represented in this forum so what follows may be superseded by someone who is a refinery chemist or an automotive engineer or whatever. I am a petroleum geochemist by profession but have never worked at the downstream (ie. refinery) end of the business:

 

1. I understand the anti-knock capability expressed in the 98 vs. 95 octane rating is achieved by an enhanced content of aromatics. Toluene is one of those but a more correct description might be "BTEX" which stands for benzene, toluene, ethyl benzene and xylenes. I assume 98 is higher in all of these than 95. All are natural components of all hydrocarbon fuels (and of coal extracts, hence the angst about CSM and aquifer waters etc). All are also pretty good plastic solvents and paint strippers (benzene is the only seriously carcinogenic one by the way).

 

The rest of the fuel is mostly paraffins - these are straight chain molecules which propagate free radicals a bit too fast in combustion and therefore tend to lead to detonation (knocking). Branched compounds and aromatics slow down radical propagation thereby preventing knocking

 

2. Aromatics are less volatile than paraffins. Hence, on storage, any loss of volatiles will occur faster for the paraffins so in theory the anti-knock capability should increase, not decrease

 

3. Paraffins are also much more susceptible to bacterial attack. This needs water and occurs quite quickly when it is present. So..if you have a little water in your fuel tank or jerry and the bugs start to eat it, again octane rating should increase rather than decrease. However..the oxidation by-products, primarily volatile organic acids, might not be good for the donk. The bodies of the bugs themselves also mean particulate content goes up.

 

It would be interesting to deliberately leave some 95 fuel to evaporate by, say, 20% of it's volume and then have the octane rating re-measured. As for AVGAS 100 without tetra-ethyl lead to get it's rating up...must be chockers with aromatics and hence more of a problem than 98 for any rubber/plastic stuff I would have thought. Unless...the refinery IS adding pure toluene or xylenes to bump 98 up...hmmm.

 

 

[facthunter]

Fuels do go off when left in tanks ' I have seen problems with fuel left in Motorcycle tanks for extended periods and some premix goes off ( 2 Stroke) so the rule is mix fresh fuel. The trouble with car fuel there is no real check for quality. Retailers can add anything to it and you wouldn't know. One servo ( big name) was apparently adding something . I had a problem with one of my cars, and after I was warned I worked out that particular garage was the one I had filled at, the 2 times that I had a problem. Nev

 

 

[biggles5128]

Bought some fuel today for the J230, took the advice of Jabiru and went with Vortex 95. I have a good relationship with my local fuel supplier, I have no doubt in what he is telling me. I am informed that this fuel does not contain any ethanol, he is going to find out what quantity of Toluene is present in both the 95 and the 98 (Caltex). I am happy to report that the engine performed just the same on the 95 as it does on 100ll Avgas and 98 mogas, no increase in CHT, or EGT. I did er on the side of safety and only poured the amount of fuel I needed for the flight plus reserves to avoid the fuel going stale over the next week , the tanks were down to minimums prior.

 

 

[Vev]

As for AVGAS 100 without tetra-ethyl lead to get it's rating up...must be chockers with aromatics and hence more of a problem than 98 for any rubber/plastic stuff I would have thought. Unless...the refinery IS adding pure toluene or xylenes to bump 98 up...hmmm.

Avgas is made from isooctane and has practically no aromatics at all ... it is highly unlikely to cause a problem to plastics/rubber etc.

 

Cheers

 

Vev

 

 

[AVOCET]

I noticed that when I fueled up for the first time a couple of weeks ago , the next day the fuel lines had expanded and felt a lot softer ,

 

Both the red silicon & the pirtec high press. rubber fuel lines , I had filled up with caltrx 98 vortex , I drained it out after a couple of days & replaced with avgas and a day or two later the lines felt normal again .

 

I re sloshed the jab tanks with kreem ( before I put the fuel in)

 

I've now got a jar with kreem lined sides & filled it with pulp 98 and so far it's stable , ill keep it in the jar for a good while to keep an eye on it ,

 

I've heard some kreem failures in the USA

 

But I think the key to a good result is to make sure the kreem has dried completely before fuel is added , at least three days at temps above20+ deg .

 

Looks like the 98 might not be all that good

 

For rubberized fuel systems ?? And jaby fuel tanks with the old type tank liner ( not kreemed )

 

Cheers Mike

 

 

[Vev]

I noticed that when I fueled up for the first time a couple of weeks ago , the next day the fuel lines had expanded and felt a lot softer ,Both the red silicon & the pirtec high press. rubber fuel lines , I had filled up with caltrx 98 vortex , I drained it out after a couple of days & replaced with avgas and a day or two later the lines felt normal again.

Cheers Mike

The impact of plasticisation will depend on the aromatic content in the fuel ... some 98 fuels have higher aromatics than others. One brand of 98 has typically only 50% of the aromatic content compered to other brands on the market.

 

Cheers

 

Vev

 

 

[AVOCET]

The impact of plasticisation will depend on the aromatic content in the fuel ... some 98 fuels have higher aromatics than others. One brand of 98 has typically only 50% of the aromatic content compered to other brands on the market.Cheers

 

Vev

Could you give me a hint about the good stuff?

 

Avgas is hard to get around hear , or a 2 hr return flight !

 

I do prefer avgas but usually end up with shandy in the tanks .

 

Cheers

 

 

[BoxFat]

Tks Nev..I learn something new every day. So AVGAS is a narrow distillation cut to isolate just the isoctane fraction (no wonder it's expensive !) and hence it would only low aromatics and cause less issues for plastics/rubber. And they still need 1/2 g per litre lead to get it up to 100 I see from Google.

 

 

[Guest Nobody]

It's worth noting that the the 100 of avgas is not the same scale as the 98 of premium unleaded. On the same scale avgas is I thin about 112 or 114.

 

 

[Vev]

Could you give me a hint about the good stuff?Avgas is hard to get around hear , or a 2 hr return flight !

I do prefer avgas but usually end up with shandy in the tanks .

 

Cheers

Hi Avocet,

 

Hawker SA right? BP Ultimate 98 is lower in aromatics in that region.

 

Cheers

 

Vev

 

 

[Vev]

It's worth noting that the the 100 of avgas is not the same scale as the 98 of premium unleaded. On the same scale avgas is I thin about 112 or 114.

98 in Aust is calculated on RON, where Avgas is done on MON (not exactly right but close enough) ... in the US Mogas is calculated on RON + MON/2 = AKI (anti knock index) number.

 

As a rough guide to align with Avgas octane nums

 

Mogas 98 RON (Aust) - 10 points ish = 88/89

 

Mogas 93 in the US is close enough to 98 in Aust ... about 88/89 MON or Avgas equivalent

 

Cheers

 

Vev

 

 

[Vev]

And they still need 1/2 g per litre lead to get it up to 100 I see from Google.

The lead content can vary a little around the world as the product is made to a standard (ASTM D910) ... inside the spec there is a methodology to test octane performance (i think ASTM D357 is used).

 

However there is a Max value of lead observed:

 

100LL = 0.56 gPb/L (blue fuel)

 

100 = 0.85 gpb/l (green)

 

Cheers

 

Vev