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Castrol GTX Magnotec Oil - GrahamM
My Mondeo TDCi 130 is going in for its first 12500 mile service this week. The local agents are offering this oil at a £10 premium. Is it worth it? Are there any advantages/disadvantages?
Thanks, Graham
Castrol GTX Magnotec Oil - Roly93
I would of thought the TDCi would use synthetic oil ?

Most diesels now have an 18,000-20,000 service interval based on this, I'm surprised that the 'fleet-orientated' Mondeo diesel doesn't.
Castrol GTX Magnotec Oil - mutley
I started a thread on this issue some time ago which was ultimately inconclusive.
My concern with the oil is that whilst it clings to the cylinder liners, having polarise molecules, this means that the metallic "crud" in the engine also clings with the oil.
Personally I have concluded it is marketing hype over practical reality and I would stick to what the maufacturer recommends.
With regard to extended service intervals my view is, within reason, the shorter the better for the now common long service intervals are cost based decisions not engineering based and assume that the fleet operator dumps the car at 60-80k miles.Long engine life is therefore not a priority
Castrol GTX Magnotec Oil - John S
Magnatec is a decent quality semi-synthetic, and your car will need at least oil of this quality. Provided the dealer is putting in the correct spec ford oil (check the handbook) - and I'd be a bit concerned if they seem to be suggesting Magnatec is better than the car neeeds - I doubt there's any benefit in paying a premium for the Castrol.

Castrol GTX Magnotec Oil - GIM

Not all synthetics are the same. The consumer definition of "synthetic" has been stretched in terminology recently to also include Group-III Mineral Oils.

The Group-III Mineral Oils have been "chemically pseudo-synthetised" by hydrocracking.

Castrol uses this 'up-graded mineral oil' as the synthetic part of magnatec.

Mobil took Castrol to an advertising tribunal but it back-fired on them. Companies can now advertise just about anthing as "synthetic" despite not being a Group-IV/V PAO/Ester base.

Castrol GTX Magnotec Oil - John S

Does this explain why some of the oils Halfords used to sell were described as 'enhanced mineral', but now appear as semi-synthetics?

Castrol GTX Magnotec Oil - GIM
Does fit the facts doesn't it!

Halfords 'own Brand' fully synthetic is however a PAO (Poly Alfa Olefin) oil...the really good stuff, not mineral oil upgraded and called 'synthetic'.

(It's really ESSO Ultron repackaged. A very high spec oil).

Castrol GTX Magnotec Oil - Roberson
Hi GIM, if you dont mind me asking, how did you find out that it was Esso ultron?

I have looked at Halfords own brand oil but can not recall them having all of the manufacturers specs (like vw 500 00 and vw 505 00) printed on the label. But esso ultron, does?. When doesn't the Halfords bottle have them on, because as you say, they are the same product.
Castrol GTX Magnotec Oil - GIM
As I work for an oil company I have of course only told you what is freely available on the internet.

Nearly all oil specs can be found if you look hard enough.

Also many other references apart from mine:




Castrol GTX Magnotec Oil - Roberson
Thanks for that GIM. I was not aware that Halfords HAD put the specs on the label.

Castrol GTX Magnotec Oil - GIM
Sorry, when I said: 'Nearly all oil specs can be found if you look hard enough'. I meant on the internet not the bottle.

For instance:
www.mobil1.com/index.jsp (look under 'Mobil 1 products', 'resource library' then 'product data sheets')

Castrol GTX Magnotec Oil - wal750
I used magnatec oil for a few years in my '93 vauxhall Corsa and would find that from a cold start in the mornings the hydraulic tappets would be very noisy until the oil got round after a few seconds. I didn't attribute this problem to the oil at first. However after changing the oil with some decent 10/40w I noticed that the tappet problem was significantly reduced.
It was almost like the magnatec seemed to 'drain away' from the tappets causing them to be noisy.
Castrol GTX Magnotec Oil - Dalglish
when I said: 'Nearly all oil specs can be found if you look
hard enough'. I meant on the internet


gim -

is castrol slx longlife 2 the exception you imply when saying "nearly all"?

or maybe i have not tried hard enough?

Castrol GTX Magnotec Oil - GIM
Castrol product data sheets:


Castrol now belongs to BP Amoco.
Castrol GTX Magnotec Oil - Dalglish
Castrol product data sheets:


i must be dim, because i just cannot find slx longlife 2 on there ?

can you ??

Castrol GTX Magnotec Oil - John S

The API and ACEA specs, plus manufacturers specs, are certainly on the Halfords fully-synth.

I beleieve this oil is also sold as Comma SynerG - Comma being a subsidiary of Esso.

Castrol GTX Magnotec Oil - Roberson
Hi John,

Thanks for that, I didn't know it came as comma neither. I must have the Halford oil mixed up with another (memory like a sieve) as I thaught that it only had the standard API ACEA specs on and no manufacturer specs.

I personally, cant use this oil as its too 'thin' for my engine. But I had looked at a 'suitable' oil from the Halfords range, but this didn't have the VW 501 01 or VW500 00 which I needed.

My local VAG specialist now uses the GTX Magnatec, so it must be OK stuff.

As for whether its suitable for the Mondeo, i'm not sure and given the option I wouldn't pay the £10 more. What do they have as an alternative. Don't Ford use Motorcraft?

Castrol GTX Magnotec Oil - Roger Jones
I had an exchange with Castrol tech services recently, during which it was declared first that "All engine type oils (fully synthetic, semi or mineral oils ) are fully miscable and will
mix readily without problems", which I queried. This was then narrowed to the "Castrol range of mineral based oils are fully miscable. However in all cases the vehicle manufacturers recommendation should be followed."

He meant "miscible" anyway (mixable to produce a homogeneous result). I'm still a bit surprised that mineral and synth should mix without problems -- only an intuitive perception based on no technical knowledge whatsoever -- although I am now less surprised that mineral and Magnatec are miscible, given what has been revealed here. On the Magnatec can it says "synthetic engineering" -- weasel words indeed.

Any more comments, GIM?

And I couldn't find Magnatec on the Castrol data list.
Castrol GTX Magnotec Oil - jc
The Ford oil for this engine is almost certainly Formula "E" which is 5w/30 semi-synthetic;a Ford dealer does not have to use this oil-Ford only require him to use an oil of the appropriate specification.Most dealers will use whatever they can get cheapest-remember they probably buy 40 gal. drums or bigger;the same probably applies to your local VAG dealer.What is not spelt out is that the dealer becomes responsible for the guarantee if non-Ford parts are used.
Castrol GTX Magnotec Oil - Stuartli
>>The Ford oil for this engine is almost certainly Formula "E" which is 5w/30 semi-synthetic>>

Ford dealerships, IIRC, should use this oil for Zetec engines such as that 1.25 and 1.4-litre units fitted to the Fiesta range to stop sticking valves.
Castrol GTX Magnotec Oil - John S

Don't know what you're driving but the CommaSynerG/Halfords meets ACEA A3 B3 API SL CF plus MB 229.1, VW 502.00/505.00, BMW Longlife 98, Porsche.

Why do you say 'too thin'? The key viscosity to meet is the second one, which is the hot viscosity, and few modern cars reqire more than 40. Don't forget oil thins as it heats, so a 5W/40 oil is as thin as a SAE5 oil when it's cold, but only thins as much as a SAE40 oil would when it's hot. Result - better oil flow when cold, but protection of the heavier oil when hot. So, putting 5W in say a car which normally has 10W shouldn't cause problems as it simply replicates what the 10W thins to shortly after start up and gets round quicker.

Castrol GTX Magnotec Oil - Dalglish
Why do you say 'too thin'?


john s - yes, i agree with you.
a lot of people seem to assume synthetic oil is too thin for their cars and will cause leaks to appear!

Castrol GTX Magnotec Oil - GIM
This article 'lifted' from the inernet makes interesting reading:
[from the Technical Manager for Mobil Oil]
The most stable products on the market and those which are being chosen by manufacturers for extended service are fully synthetic PAO (PolyAlphaOlefin). This includes Castrol SLX, Esso Ultron and Mobil 1. These products are extremely stable in extremes of performance. Next consideration is viscosity. At the low temperature end you need a 0W to give the best flow around the engine and ability to satisfy hydraulic tappets and variable valve timing. Note: 0W is not thin when cold. It is just thinner than higher numbered oils, in fact it is around 10 times thicker at 20 degrees than the oil is when at 100 degrees. So there is the case for Mobil 1 0w-40. For your interest the product being promoted by Mitsubishi dealers (Castrol Magnatec) is offered to maximise profit potential from a relatively inferior cheap product. It is a mineral oil with a small percentage of non PAO synthetic to allow the not so low rating of 10w. Sure it will work and the engine will not sieze up. But consider the longer term.
(Edited to fit on page) full text at:www.mivec.co.uk/q_and_a/q_and_a.htm

Castrol GTX Magnotec Oil - Dalglish
gim -

so what about the castrol-slx-lognlife-2 product data?

where is is ti on the net?

Castrol GTX Magnotec Oil - GIM
Castrol SLX Longlife Product Data sheet:

Speak Danish? dk.servicebooking.net/castrol/lubetable/1961_dk.pdf


Could always look yourself.
Castrol GTX Magnotec Oil - Roberson
John S and Dalglish,

Firstly, I drive a 1043cc, '93 Polo (102500miles) As mentioned in my profile.

Although the handbook was written some 13 years ago, VW 502.00 and VW 505.00 are not mentioned and therefore, it could be said that this oil is not recommended. VW 505.00 was available back then, but VW501.01 or VW500.00 is the recommended lubricants. I know that there is probably not alot of difference between them all, but why chance it when you know that the latter grades are available at great prices.

I say too thin, because it is. My tappets are noisy (only when cold) with 10w weight oils in. So a 5w is thinner still, so while the rest of the engine could probably cope well, the tappets will probably get worse. " Result - better oil flow when cold", yes this is true, but think about the other way. It probably means it flows too well, not allowing high enough pressure in both the oil pump and hydraulic tappets. This is because the the teeth in the oil pump have a grater clearance from when they were new as do the tappets. If a 10w oil "leaks" from the greater clearances too much, then even more of the 5w will. Result, lower oil pressure.

I hope you understand the blabble ive just written.

P.S. In very old engines (say 30> like in classic cars) Thinner oils, CAN, literally leak from you engine as the crank seals and gaskets were not designed to hold oils wheich are as thin as this.
Castrol GTX Magnotec Oil - nortones2
The flaw in your argument is that the w in 10w doesn't mean weight. It means the viscosity in winter. Thus there is a table of temperatures at which the oil is tested. This explains it better than I can " The purpose of the viscosity rating is to assure that, in the climate in which the engine is operated, the oil will always be able to flow through the engine's lubrication system. Eleven grades are defined. Six of them end in the letter ?W,? beginning with ?0W? and proceeding in steps of 5 to ?25W.? The W stands for winter. The remaining five grades go from ?20? to ?60? in steps of 10, without the W. In general, higher numbers mean higher viscosities.

The viscosity of the oil is tested at 100°C. Its viscosity must be greater than a minimum that is specified for each grade. For the grades without a W, a maximum viscosity is also specified. This test basically ensures the oil will perform in a warm, running engine.

For grades ending in W, in addition to the minimum viscosity at 100°C test, a low temperature test is required.  The temperature depends on the grade; for the 0W grade it is -35°C , for example. The purpose of the low temperature test is to ensure that if the oil's viscosity is low enough to permit cranking, it will also be low enough to be pumped through the engine." Source: www.sizes.com/materls/engineOil.htm
Castrol GTX Magnotec Oil - Sooty Tailpipes
A lower W viscosity is better for a noisy cold engine, not worse.
The thicker oils don't flow so easily.
I'm not familiar with the engine, but if it has hydraulic tappets, theses are like a spring-loaded piston and valve within another piston, they are filled with high pressure oil via atiny orifice, if you use a thick oil, they will take longer to 'pump up' and close the valve clearances.
Castrol GTX Magnotec Oil - Roberson

Thanks for the reply, but I already knew that W meant winter, it just some people refer to them as weight. ("quite a heavy oil" etc) There was a great series of books at my old school which explained in great detail, the subject of engine lubricants. So what you say, sound very familiar.

Sooty Tailpipes: I see where your coming from, but an engine with as many miles on as mine, will have considerably worn internal components. Is it possible that the oil will trickle out around the piston while it is being pumped in, so the clearance between lobe and tappet face is greater, hense the clacking sound. A thicker oil wont escape as readily through the clearanses. As the piston heats, it will make up this clearance by expansion allowing less of the oil to leak out.

Likewise a worn oil pump wont deliver as high a pressure with a 5w than it would with a 10w for the reasons i mentioned above.

As im no mechanic or engineer, I understand that I could be wrong.

When my car goes in for a service soon, ill tell them about the tappet and ask what they would recommend. Some people argue for thinner oils, and I see why this could help, but others have changed to thicker oil and heard the difference.

Castrol GTX Magnotec Oil - Roberson
Having thaught long and hard about this, your point would prove why some of the people who have filled their VWs with Quantum synta gold ( a sythetic of about 5w/40) have found their tappets go quiet.

Plus, a worn oil pump would make the tappets go noisy whan warm, wouldn't they?

Tut, silly me :-(
Castrol GTX Magnotec Oil - Sooty Tailpipes
While it is true that a thicker oil will give a higher oil pressure, this is only because it is restrictive in it's flow, not because it doing something useful like making the oil pump spin faster. If you put treacle in your washer bottle, you would surely have a higher washer fluid system if you see what I mean, still not much coming out the nozzles though.

While I can see that a higher viscosity oil can cushion noisy engine components from clattering, don't forget that a 5w is still 'thicker' when cold than an SAE40 when hot. Therefor if your engine is noisy when cold, but not when hot, it is likely the oil is better less viscous to make it quieter.
Castrol GTX Magnotec Oil - John S
Thanks for the support guys. I've never understood this 'synthetics cause more leaks because they are thin' argument either. As you say a 0W-40 synthetic will be no less viscous at operating temperature than a 10W-40 mineral oil, and when cold it's still far more viscous than at operating temperature. So, no problem - in fact just the benefits of better lubrication from start-up.

I wouldn't worry too much about using any modern oil in the Polo. Ok the modern specs are not listed, but any decent modern oil will be far better than those available when it was made, and that won't cause problems. As has been said, there's no problem in using modern oils with extended viscosity ranges, provided the hot viscosity matches that neded for your car.

Castrol GTX Magnotec Oil - Number_Cruncher
The other thing to remember about oil pumps is that for most engine operating conditions, they are hugely oversized - a fair proportion of the oil they pump at medium to high engine speed just goes down the relief valve, and back to the sump.

If you multiply the relief valve flow (in cubic meters per second) by the relief valve pressure (in Newtons per meter squared), you get a measure of the engine power wasted.

Castrol GTX Magnotec Oil - Roberson
Thanks for the help. I understand it all a bit better now.
Castrol GTX Magnotec Oil - Stuartli
Millers Oils compatibility guide can be found at:

Castrol GTX Magnotec Oil - Stuartli
VW's LongLife service feature apparently uses Castrol S:LX LongLife II according to:


"Castrol SLX LongLife II is a fully synthetic engine oil formulated to satisfy the requirements of the Volkswagen LongLife service regime. Not only is Castrol SLX LongLife II capable of meeting the demands of longer service intervals for both petrol and diesel engines, it is also one of the few oils that is approved to the Volkswagen Group standard for the latest generation of the ?Pump Duse? or PD direct injection diesel engines."

By the way it's usually cheaper, if you change the oil and filter yourself, to go to a motor factor - most will let you have them at trade prices.

At the moment I use National's £15 semi-synthetic and oil filter offer which has just gone up to £20 (£25 for fully synthetic).

However, I fortunately kept a £15 newspaper voucher which is valid until the end of this month...:-)

I go to the Ormskirk National outlet where the staff are very thorough; I also get the approximately half-litre not used, out of the five litres limit, for topping up purposes (only had to use it once for this purpose).

The staff pointed out I was entitled to the full five litres whichever way I obtained it.
Castrol GTX Magnotec Oil - liviococcia
Hello Members
I've been searching the net regarding 'Which is the best oil for my car', and in all the threads, and web info, advice from manufacturers and oil companies, that i've had..., i've suddenly come to the concluesion that actually........nobody really, positively, definitely...and absolutely knows the answer to this question.

You see... my car's a 1.4 VW Polo auto, it's year of manufacture is 2001, and it's a petrol engine, the thing is , the problem first lies with the 'User Manual', instead of it telling you, you need Quantum or anything else, instead it uses a VW numbering system, ..in my case it's VW500.00/VW502.00.

Now...the problem is that there are literally dozens of oil makers, with there slightly differnt ingredients, Semi or Fully sythn aswell, that also atain those VW specs to there oils, then there's also the fact that these VW specs get upgraded, but your not so sure which upgrade applies to which VW spec i.e VW501.01/502.01/505.00/505.00/505.01 and on, and on.

So the simplest solution to the problem would be, to go directly to the VW parts counter..., and ask, with chassis number in hand....., What oil does my car want?......in my case they'll say Quantum Syntha Silver 10w40 Semi-Synth, and there's your answer...., simple really!

Now.....if you start to read the views of others regarding using a thinner or thicker oil, a Fully as appose to a Semi synthetic,... worrying about reduced oil pressure or leaking seals, noisy tappets, or good/bad protection.....don't bother yourself......why i say this!..well, it was something someone said in this thread.

They mentioned something about using an oil viscosity of 5w40 over a 10w40, they said along the lines that, it's viscose latitude would cover all ambient and engine temperature eventuallities, better than the 10w40 could,....... the trouble starts when you look at the spec values for these, or any oils, .....one oil's viscose density value moving through these temperatures is very different i.e at the 40c or 100c mark, so an oil like a 10w40 will generally be denser when it reaches 40c and at 100c, than it's rival, a 5w40.

So....although you might be getting better protection when you first turn the engine on,... but maybe....just maybe, it might not be 'just so' as it gets hotter, if the oil that you decided in your wisdom to use, is not the best oil that was intended for your car's engine's engineering, through all it's unique temperature moments.

I've come to the concluesion that you don't make too much of a mistake, if you use your car makers oil recommendation,... but you stand to maybe make a bigger one if you don't.

By-the-way, i used some of that Extralube ZX1, i carn't remember if someone mentioned that here, but i found that the small addition of the stuff did make a slight difference to the level of the hydraulic valve noise in the mornings, and through it's general running.

regards all
Castrol GTX Magnotec Oil - sgarre13
Hi guys.

regarding oil specs. The engine developers develop an oil spec suitable for their engine. They get the oil companies to develop this oil and the engine developer certifies the oil for it's suitability. For instance the Mondeo TDCI engine needs WSS-M2C913-A oil. The spec is developed by Ford. The oil companies then formulate an oil which meets this spec and then Ford will certify back to the oil company based on tests that this oil meets the spec. What happens mostly is that the oil companies have a base oil stock and an additive pack. Its the additive pack which is in fact formulated to meet the WSS spec.

So a company like Texaco make the base oil and will buy in the additive pack from another company. Texaco will then put the base stock to the additive pack, bottle it and market it as suitable for Ford TDCi engines. The additive pack maker will also sell to other oil companies.

So what I'm saying is that wherever you see the WSS-M2C913-A spec quoted on the packaging, it meets the spec which Ford require for that engine. For instance I know for a fact that the Halfords 5W30 Semi synth oil which quotes this spec was actually sold in Germany as the Ford Formula E, i.e. over the Ford parts counter.

So for your Volkswagen, if they quote VW500.00 and VW502.00 you only need to go to Halfords/Motorworld and check this spec is on the back of the packaging and you're sorted.

Regarding Castrol Magnetec and Ford TDCI, I don't think the Magnetec meets the WSS-M2C913-A spec, so it is not worth the extra cash.

In case your wondering about the VW PD TDI, you must use an oil which quotes the 505.01 or 506.01 spec depending on whether you have the 1.9 or 2.0 TDI respectively. Nothing else will ensure long term durability of the sliding contact at the injector cams. However this does not mean you must buy it from a VW dealer as there are manufacturers who make it for a cheaper price (including buying the 505.01 spec oil over the Ford counter for a Ford Galaxy 1.9TDI).

Stevie G

Castrol GTX Magnotec Oil - nortones2
SG: Just one point to add. I believe you can use the 505.01 or 506.01 in either the 1.9 or 2.0 PD, or indeed the 1.4 3 cylinder. The determining factor is the duty under which the engine operates. The VW site and the handbook state what is required, but essentially, 505.01 is for annual changes, in low mileage and/or adverse conditions, or if you don't like to leave the oil in for the full period of the variable service oils:) 506.01 is for high mileage users, on longer journeys etc, in engines with the on-board oil monitor. There is also now a 507 for use with PD DPF engines, but I know v. little about this.
Castrol GTX Magnotec Oil - kithmo
The Ford spec for the Mondeo is actually WSS-M2C913-B now and although it is the manufacturers spec, it's not necessarily the best oil for the Ford engines. There are better oils, such as fully synthetics for example, that may protect the engine better but don't meet the economy requirements of the spec.
Castrol GTX Magnotec Oil - sgarre13
Hi nortones, you're right about 505 and 506 compatibility, sorry, my omission.

Kith, the durability of the Ford engines is tested with 913-B or A oil which is at the lower end of it's performance tolerance which means the retail stuff protects better than what the engine was tested with.

So I would suggest it is simply unnecessary to buy anything higher than what the manufacturer recommends. Mind you it is down to personal choice.
Castrol GTX Magnotec Oil - oilrag
"10w40 will generally be denser when it reaches 40c and at 100c, than it's rival, a 5w40."

Yes, Thats correct, I found this out a while ago on the ACEA site. From memory I think a different, lower viscosity at the `40` end is allowed for 5w40 compared with 10w40 / 15w40.
It seems disingenuous to me, to allow oils of different viscosity to be called `40`, but perhaps expains why 0w40 Mobil 1 had a high oil consumption in one of my ( older) cars when the spec was for 15w40.
Castrol GTX Magnotec Oil - oilrag
"On the Magnatec can it says "synthetic engineering" -- weasel words indeed."

I remember the late 60,s and seem to remember Castrols oil advert was `contains long chain tertiary amine tungstate`

(I also remember someone on `Sunday night at the Palladium` playing a trumpet without fingering the valves,to great applause.Trouble was, we could all do it if the music was written to the same limited range of notes)

joe public will swallow anything............
Castrol GTX Magnotec Oil - mgbv8
having polarise molecules
Expanation of ester "polar" oil


However, esters are expensive and are only used in any great quantity in race oils 20%+, Castor oil was the forerunner.
True synthetic oil PAO also use esters but around 10% and mobil use about 3% ester but use another group V oil "AN" which is less polar. Synthetics may also include mineral oil as a carrier so most oils tend to be a blend.

A 507 cutting edge oil is Fuchs Titan GT1 no zinc and synthetic esters.

A major difference between mineral and synthetic oils is that synthetics thicken less when cold and thin less when hot. Minerals have to use additives pour point depressants and viscosity improvers .

These additive can be varied for use eg
VIIs lend themselves to different applications, depending on their particular Shear Stability Index:

* The 50 SSI VIIs are most frequently used in Passenger Car Engine Oil (PCEO) applications when fuel economy attributes are critical.
* The 21-35 SSI VIIs are used mostly for heavy duty diesel engine oils and other applications with more stringent viscosity retention requirements.

Unfortunately viscosity improvers are not shear stable and get chewed up in an engine and the oil loses viscosity.
They also temporary shear which can be used to advantage for fuel economy.

Castrol startup (US Magnatec) was tested in the US and esters were lacking in the mix so perhaps the treat rate is very low.

Castrol GTX Magnotec Oil - yorkiebar
And all oils specified by the vehicle "assembler" (not manufacturer imo) are a compromise of lubrication, economy, life etc. Not only that but the specs are for a new/lightly worn engine for an average driver (whatever an average driver is?) .

A high mileage worn engine driven hard on motorways will need a different oil to a low mileage oil just used to potter into town occasionally.

There are occasions, and examples, of all sorts of engines running better , (less oil used and less noise) with older type, and thicker oils.

Ideally you should use the engine that suits your driving type and your engine.
Castrol GTX Magnotec Oil - liviococcia
This is excatly the problem.......a members quote on this thread......

""" it's not necessarily the best oil for the Ford engines. There are better oils, such as fully synthetics for example, that may protect the engine better but don't meet the economy requirements of the spec.""""

This is the sort of comment that 'muddies the waters' again!, you know the spec number, you know what oil the developers, and R & D engineers built there engine around...., but you still choose to think you know better.

I'm no longer impressed when some oil, or engine expert, says you should use 'this' instead of 'that ' oil, someone will always counter there point for there choice.

And also...VW have all these specs for there different requierment oils for each car they produce, ...now they also sell all the oils there vehicles require, they are also in the position to have the most up-to-date info regarding there engines,... god knows!... there always moving these spec numbers up another notch ...so.......

....... if my car is wanting Quantum 'Semi' 10w40, but as experts would suggest here... it will be better to run a 'Fully' 5w40,.....well !..VW have a 5w30, and maybe even a 5w40, so as long as they can sell the oil to the customer,... why, when they look at there parts computer, does it offer the 10w40 in preference, and makes no suggestion or compromise to any other suitable quality or type before the 10w40...when they so simply could, after-all they would still be selling there oil.

The fact still remains,.. that until a direction, for the oil you use for your car, comes from your car's maker directly......nothing else counts, regardless who suggests it.

...Just use what they tell you to use.....nice an simple.

Castrol GTX Magnotec Oil - nortones2
I think thats spot on, liviococcia. Lubrication is not exactly amenable to amateur advice. The usual riposte, that makers want to sell more cars, thus quote inferior oil standards to wear out the engine more rapidly, is never backed up with data, only anecdote.
Castrol GTX Magnotec Oil - mark25
Regarding the Polo:

Don't get too carried away trying to cure the tappet tapping noise with thin oil. At some point of wear/cold the big ends will start to knock lightly when cold with thin oil, b.v. Sinter Gold. This is much harder to detect than the tappets, but much worse for your engine. New tappets, or a tappet re-build would be the way ahead IMO:


Then the recomended oil, as mentioned.

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