AvGas or Unleaded?

[NT5224]

Hey Folks

 

This topic has probably been done to death but Im interested to know what fuel people opt for, and what are their reasons for the selection?

 

Do you fly with AvGas or unleaded?  I guess the main issues are  engine performance, engine wear, price and availability.

 

What do YOU use and why? Are there any major considerations I've overlooked?

 

My new engine is a Lyc 0-320 which is rated for either.  I live out bush.   Looking for other and all perspectives

 

Alan

 

 

[Thruster88]

My musketeer has a 160hp 0-320 (8.5 comp ratio) can't get a STC for mogas I think because of the airframe rather than the engine so stuck with avgas to be legal. There are plenty of pa-28's here with the Peterson dual fuel pump STC running mogas. In your hot environment avgas is probably a safer option depending on the fuel system pumps etc because of vapour lock. A petroleum engineer told me it only takes a small amount of mogas in avgas to create the higher vapour pressure. 

 

 

[bushcaddy105]

Sport Aviation, the monthly magazine of the Experimental Aviation Association has just concluded a 3-part tutorial on this very subject. Carol and Brian Carpenter write a regular monthly column titled "Technically Speaking" and the August, September and October 2019 editions have addressed this topic in great detail. The magazines are available online, but I don't know if they are only available to members.

 

As an aside, I joined to get cheaper tickets to Oshkosh back in 2009 but have maintained my membership for the wealth of technical info online, and to get the monthly magazine which I rate as the best I have ever seen.

 

My choice of fuel? Nearly always Avgas - mainly because I only have to push the plane out of the hangar to the card swipe pump. I also consider the price premium cheap insurance in that I am buying a known, safe product. I have used 98 Premium Mogas when travelling, but am wary of what it might contain. My 1980's Subaru engine was originally built for leaded fuel and I haven't had any trouble with Avgas. Oil and filter every 50 hours, and check the platinum tipped spark plugs. Never had a fouling issue in over 800 hours.

 

 

[Downunder]

Flying behind a Rotax which was designed for unleaded so my thoughts maybe off on a tangent.

 

But unleaded burns cleaner and is cheaper to buy. 

 

I have a bp card and have run avgas, ocassionally just "to see" and occasionally as a necessity.  

 

Ultimately I think it's good to be able run both as circumstances dictate.

 

I'm happy to have the option to land at the Nulabor Roadhouse and pay $2.00 odd per litre or Forrest at $3.50 per litre......

 

 

[jetjr]

expiry is the main problem with ULP, reckon theres a fact sheet somewhere on this problem

 

Only lasts a very short time, Avgas maintains spec for much longer

 

98 is a problem using volatile additives which gas off, quickly,dropping it to below 95 very quickly

 

Also I see plenty of 95 now has ethanol

 

 

[Thruster88]

I will just add, there is zero down side using avgas in a 0-320 apart from the extra cost.

 

 

[Old Koreelah]

Save a few dollars by using cheaper fuel and risk thousands in engine repairs.

 

 

[spacesailor]

Is there any restrictions on the joe public, getting Avgas, for their unregistered aircraft.

 

The question is because, when the Oaks has gone, were would I get fuel for my stationary engine runs.

 

spacesailor

 

 

[Student Pilot]

Wouldn't run normal unleaded in anything, if you leave it for a few weeks carbs become clagged, the etnanol content seems to be a negative. Premium unleaded is a lot better product. If I have a choice I'd rather run avgas even though the cost is more. I have had several aircraft with mogas stc's, in summer it becomes a pain.

 

 

[Yenn]

I have left ordinary mogas in a mower for 6 months and it fired up perfectly first try. But I wouldn't use mogas in my aircraft. Not because of any lack of faith in mogas, but I do have a lack of faith in the retailers of mogas.

 

I used to run mogas or avgas in my Corby, but I got a bad lot of mogas which caused detonation. Poor quality control. I do remember there was a time when avgas produced by one of the refinerys had to be pulled from sale and a lot of engines had to have remedial work, because of the fuel being faulty. There is far less likelihood of problems with avgas, but it is not imoossible.

 

 

[alf jessup]

I have run 95 BP Mogas in my Tecnam Sierra for the best part of 750 hours with not one issue, I regularly check it for ethanol and have never found it. Only time my plane used avgas was on a trip last year from my home in Sale, Victoria to Ayers Rock & return as unleaded was harder to source, will give it a shandy of avgas these days only if I need a top up at an out of town airport. 

 

Other than that she is strictly on a  Pulp diet.

 

 

[turboplanner]

95 is fine but the aromatics evaporate and you can have a problem starting the engine after a couple of weeks without use, however adding just a couple of liters charges the fuel enough to get an instant start.

 

Non- premium usually has ethanol in it and if left idle gums up the air galleries in the carb including the ones which have been drilled and plugged so you can’t clean them out with a wire.

 

 

[kgwilson]

I have used Mogas in my Jabiru 3300A  Gen 3 engine since new. Initially I used BP 95 & then they started adding ethanol so I switched to 98 from Shell. I always buy from a busy petrol station so the fuel is fairly fresh and it is always filtered through a Mr Funnel filter which will remove any dirt and water. I've never found anything in 4 years. I keep about 1-2 hours of fuel on board and top up with some fresh before flying if there is a break of more than 2 weeks.

 

Mogas 98 has a number of aromatics to improve its octane and clean running perspective but they do make it stink. Avgas has a fairly low odour. The aromatics include Toluene which evaporates off quickly. It will last much longer in a sealed container so long as it is full. BP did a study a few years ago and found that after 5 weeks in a vehicle tank the light components had evaporated a lot but the octane rating actually went up to 99. The result was that starting was at times more difficult and in high revving engines detonation was a possibility when under load. The detonation is not a major issue for direct drive aero engines as they are quite low revving engines but starting could be a problem. That said I've never had a starting problem attributable to the fuel. 

 

I have used Avgas when away from home as that is what was on offer at the aerodrome. I did not notice any performance difference.

 

 

[coinz]

I use Caltex 98 in my Jab,only because i usually top up the SUV at the same time i fill the jerry cans.For some time every time i used Shell diesel

 

the motor developed a rattle (diesel rattle) and i'm talking some years that went on,if i filled with Caltex over a couple of tanks the engine would smooth out,

 

back to shell and the rattle would reappear,am i going mad or is there something behind this ??

 

 

[Downunder]

Mogas 98 has a number of aromatics to improve its octane and clean running perspective but they do make it stink.

 

The smell inside the aircraft comes from the PERMEATION (https://en.m.wikipedia.org/wiki/Permeation ) of fuel through hoses and perhaps tanks. Using specifically made hoses prevents this smell.

 

I uses gates barricade fuel hose on my 5 yr rubber change and the smell went to virtually zero.

 

 

[kgwilson]

Yes the smell does permeate my vinyl ester tank but goes away after the canopy has been opened for a few minutes. Take a sniff of a can with Avgas in it & a can of Mogas 98 & the difference is huge. I haven't sniffed the automotive fuel lines which are pretty thick but I'll do this & see if it is permeating them as well.

 

 

[skippydiesel]

I have used exclusively 98 RON (at home Ampol/Caltex, BP too far away) in my Rotax 912 ULS (except on rare occasions way from home have topped off with 95 or AVGAS)

 

No problems in 10 years and 500 + hrs.

 

Carbi always clean when I do my routine inspections, no gum/H2O).

 

Engine runs a "smooth as silk" thanks to careful prop static/dynamic balance and carbi pneumatic blabance (check at each 100 hr service). No cold starting issues, can experience vapour lock after shut down/hot start (needs managing)

 

Keep my fuel in Bunnings Aerospace  20 L plastic "jerry" cans - usually top up with fresh befor flight.

 

All fuel filtered into aircraft tank and then in line gauze filters on all lines (x 3) going to engine.

 

 

[onetrack]

We've had discussions before, about fuel types/fuel brands, and people who "swear on XXX brand or grade", on other forums - and some surprising things came out - a lot from one bloke, who was a former fuel distribution company manager.

 

1. 35% of our petrol is refined overseas (largely Singapore) to Australian Fuel Standard, and delivered in tankers, ready to use. 50% of our diesel is refined to AFS overseas, mostly in Japan and South Korea.

 

2. The basic fuels are "generic". That is, they are delivered by oil tankers from the overseas refinery, or pumped from the local refinery, into the fuel farm tanks in the bulk terminals that are located in, or generally adjacent to, ports - and the various fuel companies and retail distributors draw down from those fuel farm tanks.

 

Those bulk terminals are individually owned by various companies, and sometimes a group of companies, comprising 2, 3, or 4 oil companies, plus major distribution companies.

 

It is surprising how many of our fuel terminals are fully owned by global corporations you have likely never heard of, such as Vitol, and the Australian, ANZ Terminals, who specialise in the ownership and operation of bulk product terminals.

 

So there is no such thing as "an exclusively refined Shell, or BP, or Mobil, fuel". They all draw down the same "generic" refined fuel, from the bulk terminals.

 

3. Having said that, there are "premium fuels" that have an "additive package" added to the road tanker upon filling from the bulk fuel farm. The fuel distribution manager confirmed this.

 

That additive package is exclusive to the particular fuel company, and they keep the ingredients commercially secret.

 

But it is known that numerous pricey and exotic petroleum product chemicals can improve fuel performance. Some of those chemicals you would never have heard of, such is their exotic nature.

 

Other additive ingredients are detergents (to keep fuel tanks and fuel systems cleaner), combustion-improving chemicals, fuel system lubrication improvers, and even items such as organic chemicals, typically things like plant oil essences.

 

There are active chemicals in many plants and trees that aid in fuel combustion. These chemicals are often freely released into the air, and they are called VOC's (Volatile Organic Compounds).

 

Typically, a VOC from pine trees is terpene - from deciduous trees, it is isoprene.

 

Terpene is used to produce Turpentine, Isoprene is utilised in rubber manufacturing. You can physically see the VOC's in the air from Eucalypts, they are the chemicals that produce the blue haze in the lower atmosphere, usually in the evening.

 

These additive packages are tested - in on-road actual conditions, as well as in the lab - to ensure improved fuel performance. Thus the extra few cents a litre for the premium fuels.

 

4. The quality of your fuel can be degraded by dodgy retailers adding cheaper, more-volatile or less-volatile ingredients, that reduce the fuel specification. There have been dodgy retailers caught who were adding heating oil, excessive levels of ethanol, toluene, and even canola oil, to fuel tanks in their service stations.

 

Naturally, the Govt is intent on stopping fuel scams, and they check underground fuel tanks in servos on a random and reasonably regular basis, to try and ensure fuel scams are stopped in their tracks.

 

5. By far the greatest fuel problem is fuel contamination via contaminated older underground tanks. Older underground tanks become contaminated with mud from flooding, with water from condensation, from underground water gaining tank entry via rust pinholes, and from rust inside the tank formed by the water.

 

In recent years, fibreglass tanks have become the underground tank of choice, and these are a far superior underground tank.

 

The great advantage of avgas is that it is produced to aviation requirements and specifications, and follows a fuel handling process that is tighter than mogas, to ensure the chances of contamination are virtually non-existent. Avgas contains more stable volatile ingredients to reduce the chances of vapourisation.

 

But if you must utilise mogas, buy premium mogas with reputable "name brand" oil company performance additives - buy it from fairly new servos with the latest style of tanks and tank venting and tank security - and keep away from smaller fuel distributors who can be tempted to add their own, unauthorised "additive package" to the fuel, to ensure they make more profit, rather than making the fuel perform better.

 

More info (some of which, needs updating) - https://www.aip.com.au/

 

 

[pmccarthy]

My Mr Funnel has caught brown crap In premium unleaded. stay vigilant.

 

 

[kgwilson]

I always use Mr Funnel except when getting Avgas from a bowser. I have never had an issue & the servo I buy my premium 98 is busy & recently had a tank upgrade. When I purchased my Mr Funnel the instructions said to fill it 1/3rd full with water to see what happens. Well none of the water came through so I filled it right up & still no water came through. I emptied the water & then poured in some petrol. It went through the filter like it wasn't even there. I think it cost about $50.00 but is the cheapest fuel insurance you will ever have.

 

 

[skippydiesel]

I always use Mr Funnel except when getting Avgas from a bowser. I have never had an issue & the servo I buy my premium 98 is busy & recently had a tank upgrade. When I purchased my Mr Funnel the instructions said to fill it 1/3rd full with water to see what happens. Well none of the water came through so I filled it right up & still no water came through. I emptied the water & then poured in some petrol. It went through the filter like it wasn't even there. I think it cost about $50.00 but is the cheapest fuel insurance you will ever have.

 

These days I dont see water as the most likely contaminant as long as you are obtaining your fuel from a reputable and high turnover source. Contaminants like, metal & paint flakes, rust, insects, dust or adulteration with other fuel,  would seem more likely.

 

No need to spend quit so much on a Mr Funnel - you can adapt your cheaper funnel by fitting a filter medium or even a modified in line filter.

 

 

[jetjr]

Big call Skip

 

Water is by far the most prevalent we see in vehicles and small engines fuel systems, they are buying from same bowser

 

Contaminants like you've mentioned are pretty well captured in std paper filters too - not water.

 

If you aren't using an Avgas bowser (which should have additional filtration and have samples taken regularly etc, then a water separating funnel is a must

 

Does the element in these last forever?

 

Not the document I was looking for but some info on ULP - remember these times would be ex fuel terminal

 

https://www.bp.com/content/dam/bp-country/en_au/media/fuel-news/petrol-life-vehicle-tanks.pdf

 

 

[Butch]

Also beware of buying fuel if you see a tanker doing deliveries at a servo. The large volume of fuel dumped into the tanks at delivery stir up contaminants (rust ,water, etc. ).

 

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

 

30 ks up the road the ute died and couldn't be started.

 

Outcome was a large amount of water in the fuel destroying the whole common rail system on the ute!

 

 

[Thruster88]

Also beware of buying fuel if you see a tanker doing deliveries at a servo. The large volume of fuel dumped into the tanks at delivery stir up contaminants (rust ,water, etc. ).

 

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

 

30 ks up the road the ute died and couldn't be started.

 

Outcome was large amount of water in the fuel destroying the whole common rail system on the ute!

 

The Ute manufacturer failed to provide an adequate filtration system but the owner will have to foot the $10k repaire bill, nice.

 

 

[skippydiesel]

Big call Skip

 

Water is by far the most prevalent we see in vehicles and small engines fuel systems, they are buying from same bowser

 

Contaminants like you've mentioned are pretty well captured in std paper filters too - not water.

 

If you aren't using an Avgas bowser (which should have additional filtration and have samples taken regularly etc, then a water separating funnel is a must

 

Does the element in these last forever?

 

Not the document I was looking for but some info on ULP - remember these times would be ex fuel terminal

 

https://www.bp.com/content/dam/bp-country/en_au/media/fuel-news/petrol-life-vehicle-tanks.pdf

 

Fair enough Jetjr but I tell you this - my storage system is 6 x 20L plastic jerry cans. My aircraft tanks are composite.  I always purchase fuel from high turnover servo's. In my GA days (aluminium tanks & Avgas) I regularilly drained small amounts of condensate (H2O) on my pre flight checks. In the 10 years I have been flying my little beauty, on 98 RON, I have never ever seen any trace of water in the fuel or aircraft tank drain. My filter funnel (not Mr Funnel) does trap stuff (??) not a great deal but noticeable. My aircrafts 3 in line filters rarely show any material at 50 hr inspections.

 

Just going by my experience - not scientific and not a huge survey sample to be sure but I think significant non the less..