One of the (many) idiots of which I am one on the Golf GTI web-sites aplenty has asked whether 0W-40 oil is a good bet for his Golf as he's heard a BMW ran for many hundreds of thousands of miles on it with no wear.
I said, politely, "baloney mate."
I suggested the, recommended, 20W-50 or 10W-40 and semi-synthetic.
Can anyone advise? Surely 0W-40 would be too thin at the temperatures experienced in the UK?
Also, a large number of 17 year old GTI drivers run their 13 year old 160,000 mile motas on Mobil 1!!!!! With the notorious valve stem oil seals on the Golfs they must cost more mpg on Mobil 1 than the fuel itself. Is there any point running on Mobil 1 on such a car?
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10W/40 semi-synthetic engine oil in any of these engines is just fine
Mobil 1 is only needed in perhaps highly stressed turbocharged engines.
There must be somebody who wears a white lab coat working for Mobil/Esso out there - make yourselves known!
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My understanding is the W is for the cold viscosity the other for the warm viscosity, so 0W - 40 is just runnier when cold (good?!) and the same as 10/20W - 40 when hot. So if you can afford it then why not?
Am I missing something?
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Ash, there was a thread running on this earlier this year. Consensus of opinion was that changing to a full synthetic late in a cars' life was not a good idea (oil consumption, leaks etc. IMHO I am not convinced of the benefits of these ultra thin, full synthetics, preferring a good mineral or semi-synthetic oil regularly changed.
Regards
Andrew
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Yes - the W is for Winter but surely, living in the UK the climate is never cold enough to warrant this and you may be damaging the mota by driving it with oil that is too thin - film thickness/cling/fling/pressure/flow/etc?
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Guy
The 'w' rating isn't a problem. It merely indicates that a, say 10W - 40 is the equivalent of a 'straight' SAE10 when cold (so gives good flow when cold) , but only thins to be the equivalent of an oil which is equivalent to an SAE 40 when hot, (so gives good hot protection). All oils thin with increasing temperature, it's just that multigrades thin out less than staght oils.
Regards
john
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So, what are we saying here then? That 0W-40 is bad (for older engines), not because of the 0W part, but because it is fully synthetic (or some other property not described by the SAE rating). So if a non synthetic 0W-40 was available (possible?) then it would be even better than the synthetic stuff and wouldn't necessarily cause the seal/leak problems.
Why isn't there a mineral 0W-40, after all experience usually shows mother nature knows best. If it isn't possible maybe it shouldn't be?
Confused. Me? ;o).
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There is no specific reason in terms of viscosity why you shouldn't use a synthetic in older engines, but there are concerns that using a synthetic in a high mileage engine can dislodge accumulated debris, etc which can cause problems.
It's also said that synthetics can increase leakage in older engines, but again I suspect this is due to removal of debris, and perhaps that the synthetic 'hot' viscosity is a bit lower than the mineral oil used previously.
That said many old cars were designed for use on monograde oils (eg my Minor is recommended to use a SAE30 in the UK) because that was what was available, so a 10-40 multigrade for example gives better flow when cold, and better protection when hot. I can see no good engineering reason not to use decent modern multigrades in these cars, provided the hot viscosity meets the requiremnts of the engine.
I'd be a bit wary of using really thin synthetics in gearbox-in-sump BL products, which were usually recommended to use 20 - 50, but otherwise I see no problems with modern multigrades in these cars. My Minor gearbox, designed to use an engine oil, has functioned for years on 15-50 GTX.
Don't forget a multi grade doesn't increase viscosity with temperature. A 10-40 is still more viscous when cold than it is when hot - it's just that multigrades don't thin out so much as they heat up as do monogrades. It's all to do with the molecular structure.
I suspect mineral and semi-synthetics don't get down to 0W as it's not technically possible using a mineral rather than a synthetic base oil. A 0W - 40 mineral oil wouldn't be 'better' than a synthetic oil of the same viscosity. The fact is that most older engines don't need the performance of a fully synthetic which is designed for highly stressed modern engines, turbos and extended oil change intervals. Provided it's changed regularly a good quality semisynthetic (most of which have the ACEA A3/B3 rating) will be fine and save money compared a full synthetic. Andrew Morey will confirm that he's aware of cars running on these oils which have covered more miles than the Starship Enterprise.
regards
John
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Sorry if I sound a bit thick on this one. Are we saying a high mileage engine will suffer no adverse effects if changed over to a semi synthetic.
I posed a question quite a while ago regarding my 150000 miles Carlton diesel turbo and the impression I got then was to leave well alone.
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Alyn
Wouldn't have thought so. I guess you're already using a decent mineral oil now, so a change to, say, Magnatec shuldn't cause problems. It appears the dirt loosening problems occur with the ful synthetics. Even so if you're treating the old engine with a bit of respect for its age, then you probably don't even need to spend the extra on the semisynthetic.
regards
John
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Hi John
Thanks for clearing that upJohn Slaughter wrote:
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Thanks for a detailed reply John. Doesn't matter how quick you type a long reply takes a bit of time, much appreciated.
Seems my initial thoughts were partially correct - the relatively thinner (when cold) oil lubricates better and is generally preferable. That is UNLESS you're running something of middle-aged car with quite a few miles under its belt, in which case it is TOO GOOD, as it can have too vigorous a flushing effect, (not to mention all the extra stresses involved with the reduced cushioning of worn shell bearings etc when starting from cold). This is precisely why I do regular changes with ordinary oil and dont use flushing agents in my aged BX. If it aint broke ... I wasn't intending on using anything that costs more a litre than the car's worth, but I'm not always going to be using a banger as my main transport.
Ash.
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Thanks to everyone except my brother.
I shall now return to the Golf site, plagirise all your replies and pretend to be smart!!
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I think there is a lot of miss-understanding about engine oils and what the viscosity classifications actually mean. If you ask, all manufacturers will have data about their oils for the public. Mobil 1 0W-40 has a viscosity of 13.5 cst, compared to a viscosity of around 15 for a typical 10w-40 semi-synthetic oil, at 100 degs. So yes mobil 1 is very slightly thinner than a good 10W-40 semi-syntheitic oil. VAG have not given there 501 approval to this oil, but have done so to the Mobil 1 15W-50 oil. I use Mobil 1 in the winter in my ancient Jetta 16v. Fitting a decent oil cooler to one of these cars will make more difference to the viscosity of the engine oil in hard driving than the differeence between 0W-40 and 10W40 oils.
Even the best oil such as Mobil 1 are around 7 times thicker at 40 deg c than they are at 100. 10w-40 mineral oils can be twice as thick as mobil 1 at the arbitary 40 deg mark, so just imagine how much thinker the oil is than ideal on a cold winters morning. This is where Mobil 1 will dramatically reduce engine wear- on any engine.
About 8 years ago i believe Mobil responded to people claiming that the oil was causing oil seals to fail more quickly than on engines using mineral based oils. I believe they changed the formala slightly. This issue shouldnt be a concern when using Mobil 1.
The reason why the oil seals go on the 8v GTi's, and to a lesser extent the 16v gti, is the valve guides wear. VAG did not use particularly good brass for the guides which is of the same quality on 8 and 16 valve models. As a result, on crap oil they wear out. If you just replace the seals and drive the car hard, they might only last 4k miles and the thing will be smoking again. The only way to do it is to take the head off. Many 8v cars pink, and this is often to do with oil being burnt in the cylinders. Owners of these cars also need to look into devices that can allow some mapping of the ignition timing, since some well known tuners such as Dave Walker of Emerald cams have said the highest compressin ratio you can run on poor uk fuel (97RON) on these engines is 9.8- out the factory they have a compression ratio of 10:1. This is less of a problem on the 16v due to better positioning of the spark plug.
Ben
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