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Gunk busters in petrol

old man emu

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My car is coming up to 17 years old. I recently changed the spark plugs which were probably the originals since you could drive a B-Double through the gap. The plugs were not gunked up, just a light layer of black deposit which is typical of engines running unleaded fuel. But I began to wonder about the state of the spray nozzles in the injectors. If the holes are blocked in any way, the atomisation of the fuel is poor, which results in incomplete combustion and the subsequent loss of power.


There are a couple of ways to clean the injectors. The big dollar way is to have them removed, stuck in an ultra-sonic cleaner for half an hour and replaced. The middle of the road way is to fill up with a couple of tanks of high octane petrol which is said to have gunk buster additives. The slow lane method is to add a bottle of off-the-shelf injector cleaner to a couple of tanks. Finally there is the always considered method of doing nothing, just run whatever fuel the manufacturer recommends. In my case, that's 91 octane non-ethanol.


Can the average bloke pick up that the engine is suffering from gunk build-up? Probably not. Gunk build-up is slow and insidious, like cancer. A dirty engine will cause reduced performance. According to testing by the American Automobile Association, the performance effects of a dirty engine would be barely perceptible by the driver. Dirt build-up will likely be most noticeable via a rough idle, with the biggest impact on fuel consumption because the engine is having to work harder.


All fuel contains ‘dirt’ (sediment) and sulphur, and it’s this stuff (depending on the amount in the fuel) that can cause a build-up of gunk on intake valves in petrol engines causing the engine to have to work harder. According to the latest edition of the World Fuel Charter (5th edition), which most automotive bodies are signatories to, unleaded fuel should contain no trace metal elements, only 1mg/L of sediment, no more than 30g/kg of Sulphur and that there should be added fuel injector cleaners, intake valve cleaners and combustion chamber cleaners; this is the dirt-busting additive petrol companies are referencing to in their marketing.


The devil in the wood pile is the sulphur content. While Australia’s fuel generally lines-up with guidelines set in places like the US, EU, Japan and South Korea, Australia is way out of step when it comes to the amount of sulphur in our fuel. Currently, Australian petrol contains between 150 parts per million of sulphur in regular unleaded fuel and around 50ppm in premium unleaded. However, the EU, Japan, South Korea and the US (just this year) have all had a sulphur content level of 10ppm, with some countries mandating this level in 2003 (Germany).


It is widely believed that a reduction in the sulphur content in fuel can contribute to a reduction in tailpipe emissions. Aromatics are a further contributor to tailpipe emissions which also help to raise the octane rating of fuel… In most countries, there is an aromatics restriction of 35vol%max, indeed, the EU introduced this in 2006. However, here in Australia the aromatic content of our fuel is up to 45vol%max..


In a paper submitted to the Australian Government in 2014 by Hart Energy, it was claimed sulphur content could have a dire effect on the ability of car makers to sell their latest vehicles in Australia, because of the high sulphur content in our fuel and its incompatibility with new-generation fuel-efficient and emissions-reduced engines. The Government has not adopted the recommendations (Ops Normal). There is currently a draft submission to Government that’s proposing the removal of regular unleaded from sale across the country, with many claiming it would be an instant air quality win for Australia. And it would, but would make more sense is if Australia simply adopted the 10ppm sulphur content in all fuel (regular and premium) that’s been mandated in many countries across the world.


So what do I do? The fuel I use does have cleaners added, but how much? is the question. Should I pay 20 cents per litre more for Premium, said to contain more cleaner, at a cost of $11 per 55 litre tank, or buy an off-the-shelf injector cleaner for $16 to do two tank fulls, or trust that the amount of cleaner the fuel company puts into its 91 octane fuel is doing the job?


Will I notice an improvement in fuel consumption? Not likely because unless I'm driving on a highway at a constant speed (engine RPM), my driving on local roads involves a lot of stop/start driving which laps up petrol like a thirsty drover's dog laps up cold creek water.

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A major part of inlet valve underside gunk is from you PCV system plus some  dust mixing with it if you are on dirt roads and your aircleaner not perfect. Port restriction can be considerable on some cases. The only real way to fix this is by removing the head and recondition it. Hardly ANYONE ever does this these days but most "old car" problems are head gaskets and when that happens people dump silverseal or something in and don't do long trips as you'll spend more on the car than it's worth.. Nev

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Yes I understand it's been changed lately but whether it's at the Euro figure I don't know. You'd have to ask (and trust) ANGUS TAYLOR. When you do that ask about our reserves and what's happening with the $85 million of crude oil somewhere in the US  HE purchased for US...Nev

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