On the stale unleaded petrol (gasoline) myth

[RFguy]

continuing on from above.. have been doing some reading about effects of mixture richness and detonation/preignition "D/PI". 

- chamber temperature  (piston, cylinder, head ) is a strong driver of D/PI.

- primarily, assuming the fuel is not junk, the reduction resistance to D/PI   for rich mixtures primarily comes from the cooling effect of the rich mixture. Leaner mixtures dont provide the cooling benefit of the cylinder, piston, head, glowing bits... 

- Some engines , depending on their CC design and shape, and buildup, at some RPMs, will get 'still' regions in the chamber, where despite all the gas flying around , will not get gas flow to some regions, which can become hot spots with gunk. This is more common at low and idle RPM where gas velocities are low .

 

I am sure there are others on this forum that can provide a more nuanced explanation. It is significant that AVGAS provides , for the purposes of describing knock resistance, both lean mixture equiv octane and rich mixture equiv octane (100/130).

 

 

[facthunter]

Avgas figures for Octane do not correspond with Mogas. A different reference scale is used for each one. If avgas is rated 95 it's better than mogas 95.octane.  AVgas gives a lean and rich octane rating and always did. One engine I flew behind used 130/145. That's likely not available anywhere now

  Working on and tuning a lot of older motorcycles  for many years, wouldn't think 91 mogas is safe for a comp ratio of 8/1 in an  aircooled motor with an output of 35 + HP/ litre.. Detonation will destroy motors quickly. Nev

[RFguy]

yes RON and MON, and AKI (RON+MON)/2   are different... I read they pushed the RR Merlin up to 30 lbs of boost at sea level on "150 octane".... rotax with its cool heads and moderately coolish bores the ULS  (11:1) spec is min RON95 (AKI ~ 91) and 80hp (8:1) is min RON90 / AKI 90.  chamber face of the rotax probably is ~ 130C for 110 coolant. Jabiru face is ~ 200C for 170 CHT sensor.

[Blueadventures]

Also on Rotax run on avgas don’t miss cleaning bottom of oil can. That is where  the lead stuff collects so at service do the full job and open up and clean the oil can.    Here also that lead the Decline removes is deposited on the inside of the exhaust piping.

Edited November 25, 2022 by Blueadventures

[RFguy]

Generally there is discussion on whether fibreglass tanks are ethanol compatible.

I wonder if there is any issue with volatiles and detergent compatibility with said tanks , also.  Note bulk fuel you can just buy 95 PULP, without the detergents and other marketing additives. That's probably what I would choose sans extra research. 

[Mike Gearon]

19 minutes ago, RFguy said:

Generally there is discussion on whether fibreglass tanks are ethanol compatible.

I wonder if there is any issue with volatiles and detergent compatibility with said tanks , also.  Note bulk fuel you can just buy 95 PULP, without the detergents and other marketing additives. That's probably what I would choose sans extra research. 

This is something I can reply on with some actual facts rather than the avgas/ mogas conjecture. We discuss on the Pipistrel forum and Robert Mudd is the expert at Moriarty New Mexico. He’s just shipped my motor glider from him and had him check the wings as part of an overheaul. I don’t know about other brands. I do know Pipistrel. Recent years the Pipistrel fibreglass tanks have been improved and can handle ethanol. Older ones can’t. By can’t, they start by deformation and extreme case end up looking like the wing surface has melted. It’s dramatic! Robert sent me pics. I’ll dig up if anyone is a disbeliever. That’s why I’ve decided to run exclusively Avgas in the 2003 Pipistrel. Really, it’s a motor glider and I’m hoping to regularly turn the motor off. 29:1 glide on 50ft wings. Only drama is landing the tail wheel and it’s pretty slow and tame on touchdown … (within reason)

 

Back to conjecture…. Decalin. I ran this in USA in above mentioned Pipistrel at recommended dosage. It apparently scavenges lead and it exits as dust instead of hanging around the head and in the oil. However, bloody injectors… I also read on forums it’s useless. I’ll double the dose as you mention.

[RFguy]

I bring up the question on compatibility with the detergents, volatiles and additives question because of what I saw last weekend in the banana milkshake fuel drop (same colour as the tank) ! I have seen a fuel drop in same tank type from avgas sitting around in it with no such effect.

 

Onetrack : IYO , How likely is ethanol fuel contamination into the premium unleaded fuel station supply  ? 

 

If its not ethanol attacking the tank, then what is ?

[skippydiesel]

Ref Mike Gearsons comments on ULP damaging composite fuel tanks -

 

It would seem, from US based forums I am on, that aviators struggle to find ULP without ethanol (much depends on the State legislation).

 

Here in Australia, most fuel stations (servos) offer fuel without ethanol.  So Australian pilots should have little concern regarding ethanol compatibility of fuel tanks & reticulation systems. I say a little because we all have concerns about the possibility for the fuel to be adulterated (with E10/diesel/lower RON petrol) in transit and in storage, contaminated with water/dirt/paint particles/ etc.

 

I read in this Forum that there are tests that the concerned pilot can perform on fuel, to determine ethanol content, so avoidance (for now) of the awful stuff, should not be a problem.

[Blueadventures]

38 minutes ago, RFguy said:

I bring up the question on compatibility with the detergents, volatiles and additives question because of what I saw last weekend in the banana milkshake fuel drop (same colour as the tank) ! I have seen a fuel drop in same tank type from avgas sitting around in it with no such effect.

 

Onetrack : IYO , How likely is ethanol fuel contamination into the premium unleaded fuel station supply  ? 

 

If its not ethanol attacking the tank, then what is ?

RF  source out some outboard mechanics on the coast. They will have very detailed experience of fibreglass tanks (polyester resin though) being effected by the ethical fuels.  Later aircraft are better resins and epoxy etc.  just May be interesting info.

[kgwilson]

Fibreglass resin can be a number of different compositions. The most common is Polyester and this is most definitely unsuitable for fuel tanks. The glass fibres are unaffected by ethanol. Vinylester is the chemical composition used in most fuel tanks. I cannot comment on its ability to handle ethanol. The light aromatic hydrocarbons in 98 RON petrol will permeate vinylester tanks and cause a petrol smell. They do the same for thin plastic petrol containers. Vinylester though will not melt or deform. The thicker the wall the less permeation of light hydrocarbon molecules there will be. The same goes for good heavy duty plastic petrol jerry cans.

 

I am sure that there will be a number of epoxy resins that are also good for fuel tank construction. I have done no research on these so cannot comment further.

[onetrack]

Quote

How likely is ethanol fuel contamination into the premium unleaded fuel station supply  ? 

RFguy - If all proper fuel handling procedures are followed, there should be no ethanol contamination of ULP. However, there have been some cases of ULP adulteration a few years ago, where the perpetrator was actually caught.

This means that there are still likely to be fuel adulteration practices going on, where the perpetrators have not been caught.

Typical products used in adulteration practices are used industrial volatile products, such as paint thinners, toluene, fuel tank cleanouts where the fuels have been accidentally mixed, or ancient stale fuel requiring a tank drain, etc.

These products are products that require a cost input to dispose of them, so giving them away to a dodgy servo operator is a cost saving to the business producing the volatile waste.

 

It is less likely that adulteration is going on when servo margins are high - which is not the case at present. Servo margins are now being trimmed drastically, because of the extremely high current fuel prices.

When oil and fuel prices are high, it's difficult for the servos to add on a sizeable profit - 0.5c a litre difference in fuel price can turn customers away. Average servo margins are around 2c to 3c a litre, and sometimes as low as 1 cent a litre.

In mid-2020, when the oil price bottomed right out and fuel prices dropped 30c or 40c in months, as COVID-19 impacted on travel, the servo margins increased to an all-time record of 12c to 14c a litre.

 

The greatest source of contamination in servos is rust and water from floodwaters entering underground tanks, pinholes in steel tanks caused by acidic groundwater rusting older tanks, and even sabotage by disgruntled employees.

At one time, all underground tanks were steel, coated with a bitumastic (asphalt) rust-resisting compound, and simply dropped into a hole in the ground.

 

This system failed regularly as corrosive groundwater (often aided by industrial pollution in the groundwater), perforated the tanks, sometimes after only a few years. The authorities became concerned, not because of fuel contamination - but because of groundwater contamination, as holed, leaking steel fuel tanks allowed petrol and diesel into groundwater aquifers - so tank installation processes were modified to a system where a larger hole was excavated, it is lined with geotextile fabric as a spill-containing measure, sand is laid in the excavation, and the new tank is installed on top of the sand layer.

Monitoring spears are inserted into the sand layer, so fuel tank leaks can be picked up rapidly (fuel goes out of the tank, or groundwater goes into the tank, according to the varying tank fuel levels, and groundwater pressure levels).

Fibreglass tanks are now replacing steel tanks, because steel costs are now very high, and because fibreglass is corrosion-resistant.

 

The next most common source of fuel contamination is from fungi, bacteria and mold. These form from excessively long fuel storage, and fuel storage that has allowed contaminants such as water and dirt to enter the tanks and piping.

Interestingly, the site below recommends that you do your own fuel quality monitoring. This may be easy to do when you have a business operation with your own storage tanks - not so easy to do, when filling straight from bowsers.

 

https://interfil.com.au/articles/importance-of-fuel-quality-testing/

 

Fuel tanks are monitored for fuel quality by State Govt inspectors on an ad-hoc basis, but probably not as often as they should be. Checks are random, so servo operators do not know when an inspector may roll up. A third source of contamination is bowser fuel delivery pump wear, or internal destruction, creating metal particles.

My workshop neighbour is a truckie and he recently incurred serious fuel system damage in his Isuzu diesel prime mover, via metal particles from a Costco outlet. It cost him $7K to repair his fuel injection pump system.

 

I sighted the fuel samples he kept (in two large clean glass bottles), the metal particles were highly visible to the naked eye. Costco have refused to accept responsibility, claiming they have CCTV evidence of an unknown person putting metal shavings into a bowser handpiece during the night. Seem like an odd story to me, but it may be a disgruntled employee. No-one has been caught for it, and I have not seen any police media statements where they are looking for a perpetrator, so I consider the Costco response as an unlikely story.

 

All ULP sold in Australia is refined to the Federal Australian Fuel Standard, or as amended. The basic Act is the Fuel Quality Standards Act 2000, and this has been amended to the Fuel Quality Standards Regulations 2019.

The Fuel regulations are regularly amended, and the Federal accent is primarily on fuel quality, as regards emissions and ensuring any important polluting compounds or elements do not exceed set levels.

There are many exotic, but effective, fuel additives that are banned from use in Australian fuels. Most of these exotic additives are banned because they have been proven to be carcinogenic.

 

https://www.dcceew.gov.au/climate-change/emissions-reduction/regulating-fuel-quality

 

State Govts are responsible for ensuring any fuel sold from servos meets acceptable fuel quality standards for consumers. State Consumer Affairs Depts deal with fuel contamination/quality issues where engine or other damage has been incurred.

 

Around 60%-70% of Australias petrol, and around 80%-90% of Australias diesel, is refined to Australian Standards by overseas refineries - in Singapore, Japan and South Korea. Singapore provides the largest quantity of our petrol, and South Korea supplies the largest percentage of our diesel.

Australian refineries have been steadily closing over recent years because of the ageing infrastructure, and high operating costs. The newest and largest of Australias refineries, Kwinana in W.A. was built in 1954-55, and was closed in early 2021, because the oil companies would not refurbish it. The Asian nations have been throwing trillions into refineries in recent years, so they have modern facilities and also cheaper labour costs.

 

Fuel refined to basic or "generic" 91 ULP is delivered in tankers to bulk storage facilities at various coastal locations around Australia. The bulk storage facilities are either oil company owned, or owned by companies and corporations specialising in bulk fuel storage. Oil company owned, or private-company owned fuel distributors, collect the fuel as required from these bulk storage terminals, for delivery to servos and large businesses.

 

"Generic" fuel is traded between companies and brands, and the companies or brands quite often add a "fuel additive package" at the terminal, to produce a fuel that the company can now claim is "superior" to other brands.

"Generic" fuel is sold by the cheaper "brand names" - Coles, Woolworths, and the uncommon fuel company brands, etc.

 

You will not be able to find out what is in the fuel company brand "additive package" added to the fuel road tankers at the fuel terminals - they are a highly secret concoction, comprising (small amounts) of expensive, rare and exotic hydrocarbons, all known to improve fuel and engine performance, detergents, antioxidants, anti-knock compounds, octane boosters, even terpenes from wood resin, and sometimes even essential oils!

 

The bottom line is, only initiating your own fuel testing will provide any idea of whether your fuel meets an acceptable standard for your projected use. We are very dependent on a lot of people doing their job honestly, and if profits are sought above honest and law-abiding behaviour, we as end-users are the ones who will bear the brunt of the dishonesty. The number of genuine fuel contamination claims that are reported via Consumer Affairs Depts and media reports annually is quite concerning.

 

https://www.globalspec.com/learnmore/materials_chemicals_adhesives/industrial_oils_fluids/fuel_oil_fluid_additives#

 

My fuel knowledge comes from many years of extremely high levels of fuel useage, due to a large fleet of construction and mining equipment and road vehicles, close working relationships with fuel retailers and distribution terminal managers, and personal research. 

 

Edited November 26, 2022 by onetrack

[Methusala]

1 hour ago, onetrack said:

It is less likely that adulteration is going on when servo margins are high - which is not the case at present. Servo margins are now being trimmed drastically, because of the extremely high current fuel prices.

When oil and fuel prices are high, it's difficult for the servos to add on a sizeable profit - 0.5c a litre difference in fuel price can turn customers away. Average servo margins are around 2c to 3c a litre, and sometimes as low as 1 cent a litre.

Oh no! Oldmate is at it again! Where does he troll his information from? 

 

https://www.accc.gov.au/media-release/petrol-prices-low-but-gross-margins-at-record-highs

 

The article linked above states the exact opposite of Onetrack's statements quoted above. In fact it states that gross retail margins on fuel have never been higher and that the record fuel prices charged recently have given cover to operators to hike their cut.

It states,"Across the five largest cities, annual average GIRDs in 2019-20 were 14.7 cpl, 2.7 cpl higher than last year’s average. Brisbane had the highest annual average GIRDs at 16.8 cpl and Perth had the lowest at 12.3 cpl.

Admittedly these figures are from 2019-2020 but anyone with a memory knows that fuel prices are still high and tend to rise rapidly when international oil prices lift but descend slowly as the fall.

I think that retailers for a long time have effectively snowed the public with claims that retail margins are around 2-3c/litre . Perhaps Onetrack owns a string of servo's.

 

[RFguy]

Nice writeup OneTrack . Thanks for the effort on that major treatment.

[kgwilson]

I was in NZ in July & the price there was over $3.00 a litre. The government watch dog there found that fuel companies were adding extra margin dramatically as the price increased & had reached an all time high of just over 60 cents a litre. There was a massive outcry as you would expect & the price came down to $2.60 overnight. They were still making 15-20c a litre after that.

[kgwilson]

The quality of Australian petrol is amongst the dirtiest in the world. Australia is a dumping ground for cars with poor emission control. This was the policy of the coalition government who also thought electric vehicles were a fad (remember Morrisons BS "won't tow your boat, won't run a tradies ute") & unlike most other countries had zero incentives for people to shift to electric.

 

The current standard for 91 RON in Australia is nearly 15 times lower that the current standard in Europe. The rest of the developed world is making use of Euro 6 emissions and fuel standard while we are stuck on Euro 3 for 91 & Euro 4 for 95.

 

https://www.bgaustralia.com.au/news/technical-advice/australian-fuel-quality#:~:text=The current standard for Australian,Worldwide standards for sulphur content.

[Thruster88]

Electric model aircraft have reached a very high percentage of the market with zero government incentives. GPS autosteer has become universal on farm machinery with zero government incentives. The cheapest electric car in Australia costs about 60k, someone who can afford a 60k car doesn't need a government hand out. 

 

The fuel quality article was written by a snake oil salesman, it might be very good snake oil.  

[onetrack]

Methusala, I don't know what you read in my article above, but I stated exactly what you have said - servo gross margins were at all time high in mid-2020, when petrol prices slumped to a bit over a $1 a litre.

Accordingly, with the high prices today, nearing $2 a litre, servo margins are now being squeezed. I read the same article you read and linked to.

 

You might want to read the answer posted in the link below, by Adam Donnison, on this fuel margin question page on Quora. Adam owned more than one servo in Victoria.

 

https://www.quora.com/What-is-the-profit-by-product-for-city-and-suburban-petrol-stations-in-Australia

 

You can find the Terminal Gate Price for petrol and diesel on the AIP site for each week. These are the daily going fuel prices if you rock up to the terminal to fill your road tanker - it's also the price the smaller fuel retailers have to pay.

Obviously, deals go on between brands and servos, and the retail price of fuel is sometimes below the TGP. This is due to discounting between the oil companies and service stations.

If you look at the TGP's for each day and compare them to your local servo prices, you will see the margins are currently pretty slim. As I stated, slim retail margins are likely to lead to fuel adulteration, particularly amongst smaller retailers.

 

https://www.aip.com.au/pricing/terminal-gate-prices

 

As to owning servos - No, I've never owned a servo in my life, but I probably should have invested in a fuel distributorship many years ago.

In the mid-1990's, our family mining contracting company was purchasing over $300,000 worth of fuel a month. We were the largest family-owned mining contractors in W.A., in 1994 - only the corporate operators (Roche Bros, Brambles Ltd, Leighton Contractors, Eltin Ltd) were bigger.

 

Edited November 26, 2022 by onetrack

[kgwilson]

3 hours ago, Thruster88 said:

Electric model aircraft have reached a very high percentage of the market with zero government incentives. GPS autosteer has become universal on farm machinery with zero government incentives. The cheapest electric car in Australia costs about 60k, someone who can afford a 60k car doesn't need a government hand out. 

 

The fuel quality article was written by a snake oil salesman, it might be very good snake oil.  

Doesn't matter who wrote the article. Australias emission standards and fuel quality are poor by standards set in first world markets as are the emission standards of imported motor vehicles. Government handouts have nothing to do with actively discouraging where the future lies. By 2035 you will not be able to buy an ICE engined car. You can choose to ignore the facts if you like.

 

https://www.abc.net.au/news/2021-10-14/australia-dumping-ground-for-polluting-cars-euro-6-standards/100535418

[Thruster88]

7 hours ago, kgwilson said:

Doesn't matter who wrote the article. Australias emission standards and fuel quality are poor by standards set in first world markets as are the emission standards of imported motor vehicles. Government handouts have nothing to do with actively discouraging where the future lies. By 2035 you will not be able to buy an ICE engined car. You can choose to ignore the facts if you like.

 

https://www.abc.net.au/news/2021-10-14/australia-dumping-ground-for-polluting-cars-euro-6-standards/100535418

Perception and reality may be different with regards Australian fuel quality. 

 

 

“The majority of the BMW Group Australia fleet, including our range of new models, has been certified to run on Euro 6 fuel standards for some time now. Locally delivered engines in BMW and Mini models achieve the required power, efficiency, and emissions figures when using Australian fuel without any issues,” Ms Blanckenberg said.

 

“While we would certainly welcome a lift in fuel standards and quality in the future, we are able to provide our customers with vehicles that perform to an optimal level with the current (fuel) offering.”

 

BMW said recently that although it was prepared to offer electrified vehicles across its range as soon as was required, it was in no hurry to abandon development of its combustion engines and was confident customer demand will continue into the future.

 

But for Mercedes-Benz, impending Euro 7 emission standards were already sounding the death knell for many of the combustion engines offered in its range. 

 

Mercedes-Benz chief operating office Markus Schafe recently told British publication Autocar that the brand “will reduce the number of engine variants, going through Euro7, by about 50 per cent”, but said it would only completely cease development and production of the combustion engine “where market conditions allow”, and possibly by as soon as the end of the decade.

 

The German manufacturer has already announced plans to end production of its V8 and V12 engines, switching to high-output and electric-assisted four-cylinder units across much of its future range – including the next generation AMG C63 sports sedan, a crowd favourite in the Australian market.

 

Despite the gloomy news, Australian consumers can rest easy in the knowledge that the current crop of Mercedes-Benz passenger vehicles already provide the best environmental performance possible, with Mercedes-Benz Cars Australia media relations and product communications manager Ryan Lewis telling GoAuto that the quality of Australian fuel was not a limiting factor in meeting the latest Euro 6 emissions equivalent.

 

“Currently, every Mercedes-Benz passenger vehicle sold in Australia is fitted with a Euro 6 compliant engine, and all are suitable for use with today’s Australian fuels,” Mr Lewis said.

The Grattan Institute suggests capping vehicle emissions could be another strategy that would set Australia on the road to net-zero emissions but states that better quality fuel is required to help achieve that target. 

 

https://www.goauto.com.au/news/conflicting-claims-about-australian-fuel-quality/2021-11-01/86245.html

[old man emu]

There is a class action against BMW https://www.law.com/international-edition/2022/10/21/australia-class-action-firm-plans-cases-against-bmw-and-mercedes/?slreturn=20221026163158 and a similar one against Toyota for schemes in which devices were installed into diesel engines to manipulate lower nitrogen oxide (NOx) emission levels when under testing in order to pass regulatory requirements.

 

“Consumers have likely been misled, many likely having purchased these vehicles for the environmental benefits,” Malouf said. “I personally am, and without doubt, all class members are, surprised and very dismayed that major international companies who purport to be acutely environmentally conscious with worldwide brands would allow environmental damage on such a major scale,” he continued. “It is an outrage and most importantly GMP Law intends to pursue the maximum punitive damages possible as a future deterrent.”

[RFguy]

anyways ........

 

discussion is on truth or myth stale ULP.

My current thinking is that the ULP becomes contaiminated by aircraft  tanks, ethanol, etc

[Methusala]

11 hours ago, onetrack said:

Methusala, I don't know what you read in my article above

Onetrack, I post on this forum when a. I think that my experience can be useful to other readers, and b. when something strikes me as being either false or deliberately misleading. I am used to the mainstream media deliberately misleading and why not? They are after all owned by the rich and powerful.

In this case I noted that you gave no attribution for your claim that fuel retailers operated on ridiculously thin margins. The fact that the best information I could find was a year out of date is perhaps not surprising. Who is going to bell the cat. As for quoted info on 'at the depot' pricing , supplied by the industry, that can be easily manipulated if not intentionally misleading.

Recently, when traveling to Tumut, I found the pump price for unleaded 91 was 10c below the best price available in Canberra. This shoots down the argument that high volume results in lower margins.

I apologise for my fishing comment regarding your possible links to servos. But being obviously busy, keeping up with every topic is very time demanding. No one knows everything, not even (ahem) me!

Many fishy things about the fuel industry including the restricted number of major participants. Coles and Woolworths , in particular, are huge retailers but have meant bugger all in terms of discounting grrrr! The fact that increases in prices occur almost instantaneously over an area lead me to believe that fuel is sold on consignment and the majors dictate prices to the stock holders. This leads me to be sceptical on the evidence you quoted of prices 'at the distributors gate'.

As on many things we will just have to agree to disagree. But don't be sucked in by mass media sources; seek information widely. Don

 

[Flightrite]

Good job our A/C engines are of an agricultural design and would run on chook poo if ya could get it in there😂 I worked for Mobil for many years whilst building hours, good job the general public have no idea what goes on in the industry.😉

Edited November 26, 2022 by Flightrite

[Blueadventures]

52 minutes ago, Methusala said:

Onetrack, I post on this forum when a. I think that my experience can be useful to other readers, and b. when something strikes me as being either false or deliberately misleading. I am used to the mainstream media deliberately misleading and why not? They are after all owned by the rich and powerful.

In this case I noted that you gave no attribution for your claim that fuel retailers operated on ridiculously thin margins. The fact that the best information I could find was a year out of date is perhaps not surprising. Who is going to bell the cat. As for quoted info on 'at the depot' pricing , supplied by the industry, that can be easily manipulated if not intentionally misleading.

Recently, when traveling to Tumut, I found the pump price for unleaded 91 was 10c below the best price available in Canberra. This shoots down the argument that high volume results in lower margins.

I apologise for my fishing comment regarding your possible links to servos. But being obviously busy, keeping up with every topic is very time demanding. No one knows everything, not even (ahem) me!

Many fishy things about the fuel industry including the restricted number of major participants. Coles and Woolworths , in particular, are huge retailers but have meant bugger all in terms of discounting grrrr! The fact that increases in prices occur almost instantaneously over an area lead me to believe that fuel is sold on consignment and the majors dictate prices to the stock holders. This leads me to be sceptical on the evidence you quoted of prices 'at the distributors gate'.

As on many things we will just have to agree to disagree. But don't be sucked in by mass media sources; seek information widely. Don

 

In Mackay the price of 91 fuel is at least 6 cents and usually 10 cents cheaper on the north side of the river, go figure.  I live on the north side and have a laugh at the prices.  Most people won't go looking for cheaper or look at webb price.   When growing up a mate's dad had a BP on north side of Brisbane and he would drive the main road a few times a day a check the competitor's price then come back and under cut them also increase his price if they were high.  

[onetrack]

Quote

My current thinking is that the ULP becomes contaiminated by aircraft  tanks, ethanol, etc

Glen, the basic problem as regards petrol is it's a combination of a large number of relatively unstable hydrocarbon compounds, and nearly all of them quite volatile. So, according to basic high school chemistry, unstable compounds easily break down, or form new compounds. Add in major temperature variations, and some minor contaminants, and you have the catalysts for chemical compound breakdown and change.

 

Is aluminium reactive to petrol? No - not under perfect lab conditions. But add in a small amount of water to petrol that has been in contact with the ground - then include other chemicals in with that water (such as rust particles, and dissolved, naturally found mineral compounds, that are common even in our drinking water) - then add the slightly contaminated petrol to an aluminium tank - and you have a cocktail whereby unplanned chemical reactions will occur, and the hydrocarbons will start to form new, undesirable compounds.

Rust contains many highly unstable iron compounds, of which many will react with unstable hydrocarbon compounds to form undesirable chemical contaminants.

Fuel ages rapidly, and this is why fresh fuel is always advised when stable performance is sought - and why fuel storage methods, and fuel handling care, is critical to ensuring your fuel stays clean, and does not lose important volatile fractions.

 

Below is a link to an SAE short article on aluminium aircraft tank etching caused by minor contaminants in the fuel.

 

https://www.sae.org/publications/technical-papers/content/400142/

 

I've just recently acquired some petrol drained from my stepdaughters XJS V12 Jaguar, that she inherited from her deceased father, who lived in Darwin. The Jag was shipped from Perth around 2016, and rarely driven. Her father died in late 2021.

We shipped the Jag back to Perth, and she's been trying to get it into a satisfactory running condition. It wouldn't run smoothly despite much engine work on electrics and the early Bosch mechanical fuel injection.

 

The fuel was finally condemned as suspect. The tank drain revealed petrol that looked almost like diesel. It also contained a quantity of water and rust. Poor fuel handling and poor storage would have been the primary contributors to the poor state of the petrol. Large amounts of the volatile fractions are long gone, and the fuel is highly discoloured, due to chemical reactions.

 

As far as ethanol contamination goes, nothing is guaranteed in fuel handling processes. I've seen a country fuel depot manager accidentally mix petrol and diesel in the ground level depot storage tanks, when unloading fuels from a train tanker.

He merely diluted the accidental mix with a lot more petrol, and sold it on. No-one was the wiser.

 

In earlier times here, the BP refinery at Kwinana sent major quantities of refined diesel and petrol and kero via ONE pipeline, from the refinery, to the fuel storage farm at North Fremantle. How did they do this? The refinery used slugs of WATER to separate the fuels being pumped!

At the fuel farm end, they would simply drain and filter off the water, and then go on to the next type of fuel being pumped. Few people know that under the Fuel Standards Act, there is an allowance in the fuel testing, for a tiny percentage of water in refined fuel.

 

I hate to think about the level of rust inside the Kwinana fuel supply pipeline that was used from 1955 to 2021 without replacement. Despite substantial filtering in fuel handling, contaminants still get through, and it's the dissolved contaminants that is where many of the problems start. The degradation may be slow from those contaminants, but it's steady.