Synthetic Engine Oils

I was going to raise a more general question about Synthetic Engine Oils, but noted this was largely the same topic here but couched around Subaru.

My reading about Synthetic oils is: they last very much longer than crude oil derivatives. So long, some say, that you don’t need to change the oil EVER, only the oil filter, at around 10-15000 miles ie 15-20000kms!

That mechanics put the oil change sticker just to get more business, an unnecessary service.

Has Choice investigated this?

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Edit added comment in response to

_Whether we agree on extended service intervals, or not, the mechanic if they were asked to indicate other than the manufacturers recommendation is unlikely to do so. It is a potential liability that would be expensive and complex to defend if a customers vehicle subsequently failed outside the OEM recommendation. _

We are all free to make alternate decisions and only book the next service to suit. In doing so we take on the risk. And unfortunately general advice that may come from a good source needs to be qualified to ensure it is appropriate for your individual needs. Similar to the qualifier on financial services information.
End of edit

A high risk business strategy. Charging for oil that is not replaced. Potentially a criminal offence?

Even the highest quality synthetic engine oils after 10-15,000km will appear, smell and possibly even feel very different on the dipstick when compared to a fresh new oil sample.

Having a reliable honest mechanical service provider may be the best solution for the average consumer. Knowing you have one? The state based motoring organisations do list approved mechanical service providers.

On not changing oil over a long period of time. Changing the oil filter is not a solution as the filters only remove coarser contamination. Providing the oil level is regularly checked and topped up, anecdotally it can be many tens of thousands of kms before there is any other evidence. Often gummed up oil control rings, increased oil consumption and a smoky exhaust. Increased and obvious rattling noise from the top end (cams and valve gear, excuse simplification) is also a common symptom of lubrication neglect. For turbo charged engines the symptoms may be more severe and permanent. And who knows what else?


You are shooting the messenger, that is why we need Choice to speak, we have opinions here, that don’t agree on the facts.

There are many posts on many sites, mostly from the USA, about Synthetics, and I have summarised them. They don’t agree with your opinion.

I am not implying that mechanics are not replacing oil, just doing so unnecessarily, via their reminder labels, based on out of date concepts.

Synthetic Oils are designed to stop all the things you list over a long period.

IMHO, based on extensive experience with a range of vehicles as well as oil testing, 10k km is a perfectly good service interval particularly if you’re using synthetic oil. Certainly there are some cars that call for it more regularly but they’re typically specialised, high performance and turbocharged; my twin turbo Nissan GTR mandated 5k and that’s as low as I’ve ever seen.

A 6 month service period for a standard passenger car is disgraceful. I currently have three vehicles made on three continents for which the manufacturers recommend 15k/12 months, two of them are high performance and one is commercial. All are considered robust and reliable by design.

If you’d like to talk to the oil manufacturers you’ll find their tech folks extremely helpful. The technology in modern oils is pretty amazing so unless you’re doing track laps with a local motorsport club, in which case it should be changed at the end of each event, such frequent changes simply aren’t required. Perhaps the only other case is when doing regular short trips that don’t warm the engine as this means the condensation in the block isn’t getting hot enough to evaporate, although modern cars warm up quickly these days so the trip would need to be less than it takes to have the temp guage reach its normal range for about 10 minutes.

The term ‘Australian conditions’ always cracks me up. I guess it doesn’t get hot in Arizona or New Mexico like it does here, and would that be conditions in Darwin or the snowfields?

Sorry OP that doesn’t help your situation particularly re warranty, as others have suggested you might like to consider looking for an independent garage as soon as warranty expires.


Apologies, I appear to have read your post another way.

Agreed there are some significant challenges here.
One relates to the quality, cost and reliability of servicing providers.
A second relates to the recommended servicing requirements, and whether they are reasonable, or excessive.

The motor retail, support and marketing business is a financial beast turning over close to $200B annually. It has had a lifetime of free reign aside from a handful of safety initiatives such as seat belts.

It is a worthy target for consumer scrutiny. The state and national motoring associations seem not to have been active or successful in holding the industry accountable. It is a big ask?

I will hold to one point. There is no one size fits all solution for servicing based on time or distance if you wish to optimise the financial outcome.

Worse, is that some owners are happy to extend servicing and neglect maintenance, happy to dump the second hand car before it becomes too self evident. Others pamper their pride and joy and hope to have many trouble free kilometres.

I would not dispute the longer life of the base oil component of a synthetic oil formula.

It is important to also consider the additive package included with the oil package. It has a finite life.

No two cars are identical. No two cars achieve the same number of kilometres exactly the same way.

In that instance it is possible to relate fact or opinion and find examples that match either well. Equally there are as many if not more alternate and contrary examples to hold up.

We service both our cars now once a year only, and are close to 200,000km on both. The oil grades are as per handbook. Neither are a full synthetic product. Distance travelled varies between 10,000km and 15,000km annually. We’ve had two Subaru’s with one happily reaching 150,000km on standard services, while another we know well reached 200,000km on only one annual service once out of warranty. All used non dealer servicing post warranty.

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Why wait? As long as a service is by the log book by a reputable shop (approved by an auto club or member of state body such as VACC?) and so documented, it fulfils warranty requirements. Having gone that route the shop (and I presume most shops these days) subscribe to data services that enumerate warranty services and produce quite detailed invoices regarding same. My service invoices from my independent show everything required from the log book having been inspected or replaced, per log book requirements.

Any shop that does not have that ability might be best avoided during warranty for administrative reasons if no other. A hand written ‘20,000km service completed’ may not be as convincing proof as the explicit invoices I receive.


Australia’s climate is very different to the US climate. For example, the average mean temperature for the US is about 12°C, while in Australia it is about 18°C. While some locations in the US may be as hot (even potentially hotter) as parts of Australia, they are not as wide spread. In general the US winters are also vastly different and significantly cooler to that in Australia. This is due to a number of factors, with the most obvious that the US sits on average further north of the equator that Australia is to the south.


I’ll agree with @Mustang’s amusement. Australian conditions are different but climate is not one that should matter. Both continents are diverse with diverse climates although North America has greater extremes, especially in winter. Since people live in places not across an entire continent, re climates Melbourne is much like San Francisco, Sydney like Los Angeles, Cairns like Houston or Miami and on it goes. Do we have areas like Minneapolis? The Snowies should qualify for a few hours a year :slight_smile:

Some things are different here compared to the US such as road surfaces; ours are harsher being a lower cost mix and Americans don’t have an appreciation of our outback tracks unless they have been on one, but same goes for most of us. There are others differences one can hang a hat on, but I do not agree climate is one of them.

‘Australian conditions’ claims remind me of this era in Japan.


Indeed, technically you shouldn’t have to use dealerships for the reasons you state. However, I still maintain that it’s worth doing while the car is in warranty. It’s very easy for a dealer to initially push back on a claim (and they vary on this greatly), even though you know consumer law supports you there’s no means by which to compel them to do anything in a reasonable timeframe. So your car sits there broken while you spend a fortnight chasing them in the hope they’ll do the right thing, and after you realise they’re simply going to dig in you spend another month waiting for the matter to be listed with the relevant tribunal for remediation, and after that it may be listed for a hearing. By this time you’re exasperated, your car has been immobile for a couple of months, and you face the prospect of a hearing that doesn’t meet your expectations. Even if it goes your way you face the prospect of having it repaired by a dealership that may be inclined to do only the barest of work to fix the problem, over several weeks instead of days because it’ll be treated as a ‘fill in’ job.

Dealer servicing hurts - especially at 6 month intervals! - but I reckon it’s worth the short term pain in cost compared to the inconvenience and anxiety that could arise if you tried to make a claim having used an independent garage.

Would be interesting if some folks called (or better emailed) their servicing dealer or car company and asked what their respective positions would be, the responses could be interesting.

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I would be quite surprised if any quoted something different from the law, even if the response included the benefits of dealer servicing, and there are a few beyond those you put forward.

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Hi @longinthetooth, I’m sure plenty of us would love to see this type of test. I’ll be sure to pass it on to the investigations team.

I decided to move this to a separate thread as I thought it would allow a better discussion on this specific issue, hopefully you don’t mind.


Edmunds is a reliable motoring source. They have this to say

and Consumer Reports, Choice’s American sister (?)


@PhilT, great links.

I see the US Comsumer Report states…

It’s not just about miles: If you don’t drive your car a lot, your oil still needs to be kept fresh. Even if you drive fewer miles each year than your automaker suggests changing the oil (say, 6,000 miles, with suggested oil-change intervals at 7,500 miles), you should still be getting that oil changed twice a year.

Why? Oil becomes less effective as it ages, and by not getting the engine warm enough, excess moisture that forms in the engine will not be removed, which can lead to shorter engine life.

Which is consistent with what many car manufacturers say for their vehicles in Australia.


US owners manuals usually have a special clause for ‘severe service’ by whatever name, that include ‘not much driving’. Those service standards are usually 6 monthly when the regular service interval is usually annual these days.

A difference worth mentioning is that across the US you can get drive in oil changes for $30-70, unlike here where they are far dearer and you need to book ahead.


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And therein lies the value of conducting a random survey. Those of us who think they know the results - either way - might be surprised. This isn’t a matter of whether dealerships should or shouldn’t be complying with the law, or can be compelled to do so, it’s a matter of how compliant they’ll be.

Would any response document that they were knowingly breaking the law, regardless of how they would respond when asked? Any who replied there would be a problem would be off my list for gross stupidity.

I trust they wouldn’t provide a response that implies an intent to break the law. I think we can leave that aside for now but it would be interesting to know if this happened :grin:.

The test will be to see how forthcoming they are in providing unequivocal responses affirming that there is absolutely no issue and warranties would be honoured despite vehicles not being serviced at dealerships, provided service intervals and procedures are carried out by a licenced mechanic etc etc. If it were that simple dealer service departments would go broke charging twice or more times the price of independents.

It is that simple…see…

The ACCC also has information on their website in relation to consumer rights in relation to servicing of vehicles…

Any dealer advising that servicing must be done by an authorised mechanic/dealership to maintain warranty is potentially breaking the Australian Consumer Law. Action was taken against Apple by the ACCC due to conveying similar information to its customers about unauthorised repairs to its products.

As long as servicing is done by the independent mechanic in accordance with the manufacturer’s service manul/requirements, there will be no issue. The independent mechanic should also endorse/stamp the vehicles service manual and fill in the other required details (e.g. mileage, date etc) as evidence the service has been completed as required by the manufacturer. If non-genuine parts are used by the independent mechanic in the service and one fails, then it is a warranty claim against the independent mechanic. Should the independent mechanic use genuine parts and these fail, one can make the warrnty claim against the manufacturer and the warranty work can be done either by the independent medhanic or the manufacturer’s service centre. Most vehicle warranty claims arise from a part installed on the car manufacture failing irrespective of who and where servicing occurs. The car manufacturer is still responsible and required to honour the part’s warranty. If a mechanic can’t service a vehicle, say due to not having the right service computer, unable to get service information from the manufacturer or it is outside the capability of the mechanic (e.g. a very expensive supercar with unusual parts and service requirements), the mechanic should indicate such and one should look for a service elsewhere.

If one choses to pay more for a service at a dealership/manufacturer’s service centre thinking that it is better, then that is one choice. We and other famiky members will continue to use a local independent mechanic to service our vehicles in accordance with the manufacturer’s service requirements. BTW, we have made hassle free warranty claims with the manufacturer even though we service by a independent mechanic. Our mechanic even did one of the warranty claims/repairs for us after Subura Auatralia gave the go ahead as it could be done more easily and conveniently at one of the routine services.

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Thanks for the Edmunds links. Also thanks @BrendanMays for forwarding to the Choice team. These links support my initial summation of what I read about synthetic oils. Jaguar 15000 miles, ie 24000kms; most others 10000miles - 16000Kms.

Of course there are exceptions, but let’s first get some agreed facts about the Norm.

Many of the comments here sound just like those in the Endund’s article, people in denial, that oil technology has undergone radical change in recent years. Be conservative, don’t trust new R&D, Australia is harsher than most other places. If it is harsher it isn’t the continent it is the lazy people who would rather drive 1km to the local shop than walk or ride a bike, everything says that is the best way to damage oil and engine.

I hope the Choice investigation also looks at the impact of retaining synthetic oil and only changing the filter, ie, does the filter increase the longevity of the oil even beyond the 16000- 24000km requirement.

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I wish you well if you ever have a warranty claim without a dealer service history, you’re in an excellent position to advise them on what should happen. Do let us know how it goes, particularly if it’s a major repair on a prestige vehicle and the dealer obliges with minimal resistance. This is now a synth oil thread so I won’t be posting further here on this.