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Discussion Starter · #1 ·
Sorry to bring this old issue of oil (but don't we love to talk about it - I think it gives us a good feeling about doing the best for our beloved engines).
My local motor factor is selling the new Vauxhall fully synth 5/30 for £18. I have been using 5/40 Halfords for a while. I note that 5/30 is listed in the handbook. But what does the panel think?
 

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Mmmm ... What do we all think of Vauxhall?


I'll get me coat !!

On a slightly more serious note & not knowing the history of the oil you've used, if you have never used fully synthetic oil in your engine, switching to same can result in oil leaks. If you're using semi-synthetic you may choose to remain with this type of oil for your engine. If you can switch to fully synthetic oil without problems then that has to be a good thing. Especially if yours is the Turbo though for me, Mobil 1 is the only oil I'd use. (Personal choice only).

Cheers.
Mally
 

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Discussion Starter · #3 ·
What do we think of Vauxhall? Why...they're our saviours. What would we do without them? We'd be nothing, despite all the complaining.
Again, on a more serious note. I wasn't questioning the merits of synthetic versus semi or mineral. I've been using Halfords fully synthetic for some time without complaint (or leaks, thankfully). I do 3000 fast miles a month, so I do an oil change every two months. I want a high performance oil at a reasonable price.
My question related to actual grade. I had been using 5/40 fully synth and I wonder if 5/30 would do any harm?
 

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I have just started using it, the guy next to me at work is in the Vauxhall car club and managed to get me a box of 4 x 5L cans for £42! I figured if Saab specify a 5W30 oil as acceptable it should be fine to use it.
 

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Ah the old synthetic question. Well, be careful because the word "synthetic" no longer means what it used to. Most cheap oils labelled synthetic are not, they are petroleum oils. These lower grade oils are produced by a process called "hydrocracking".

The true definition of a synthetic is "built in laboratories by chemists" and not dug out of the ground. The only true synthetics from a chemists point of view are poly alpha olefins and esters.

These are commonly referred to as pao (group IV) and esters (group V) basestocks and are the best lubricants available although the cost more.

This piece by Silkolene/Fuchs Chief R&D Chemist explains the background to this confusion.

A word of caution – You get what you pay for!

Below is an article written by John Rowland, Silkolene/Fuchs Chief R & D Chemist for 40 years.

Quote:

Costs of synthetics vary considerably. The most expensive are the “Ester” types originally only used in jet engines. These cost 6 to 10 times more than high quality mineral oils.

The cheapest synthetics are not really synthetic at all, from a chemists point of view. These are in fact specially refined light viscosity mineral oils known as “hydrocracked”. These have some advantages over equivalent mineral oils, particularly in lower viscosity motor oils such as 5w-30 or other oils with a low “W” rating such as 5w-50 etc and they cost about 1.5 times more than good quality mineral fractions.

We use several different grades of this base oil, where appropriate. This is the “synthetic” which is always used in cheap oils that are labelled “synthetic”.

Yes it’s a cruel world, you get what you pay for!

Now, you may ask, why are these special mineral oils called “synthetic”?

Well, it was all sorted in a legal battle that took place in the USA about ten years ago. Sound reasons (including evidence from a Nobel Prize winning chemist) were disregarded and the final ruling was that certain mineral bases that had undergone extra chemical treatments could be called “synthetic”.

Needless to say, the marketing executives wet their knickers with pure delight! They realised that this meant, and still does, that the critical buzz-word “synthetic” could be printed on a can of cheap oil provided that the contents included a few percent of “hydrocracked” mineral oil, at a cost of quite literally a few pence.

So, the chemistry of “synthetics” is complex and so is the politics!

The economics are very simple. If you like the look of a smart well-marketed can with “synthetic” printed on it, fair enough, it will not cost you a lot; and now you know why this is the case.

But, if you drive a high performance car, and you intend to keep it for several years, and maybe do the odd “track day”, then you need a genuine Ester/PAO (Poly Alpha Olefin) synthetic oil.

This oil costs more money to buy, because it costs us a lot of money to make, very simply, you always get what you pay for!

Unquote:

Hope this explains.

Cheers
Simon
 

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So..... what do we need to be using. Anyone want to name (and shame) a few names. Or is it mobil 1 or nothing. The biggest scam with mobil 1 and why they don't sell as much as they could IMHO ( after retailing oil for 20 years), is that they pack in 4 litres and not 5. Tons of cars need more than 4 litres so an oil change is in the region of £40 + filter because you have to buy a 4 and a 1 litre. That is why many potential customers look around for a cheaper alternative although they are sold on fully (proper) synthetic.
Is the VAG fully synthetic i.e. as in Mobil 1?
 

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You can pretty much guarantee that low viscosity oils are synthetic or are hydrocracked oils with some pao added to reach the low pour points required for API/ACEA on 0w and 5w oils.

ALL semi-synthetics are hydrocracked and most oils of 10w, 15w, 20w etc are not synthetics with some noteable acceptions.

Basestocks are blended to meet specs so the waters are well and truly muddied.

All oils are comprised of basestocks and additives. Basestocks make up the majority of the finished product and represent between 75-95%.

Not all basestocks are derived from petroleum, in fact the better quality ones are synthetics made in laboratories by chemists specifically designed for the application for which they are intended.

Basestocks are classified in 5 Groups as follows:

Group I

These are derived from petroleum and are the least refined. These are used in a small amount of automotive oils where the applications are not demanding.

Group II

These are derived from petroleum and are mainly used in mineral automotive oils. Their performance is acceptable with regards to wear, thermal stability and oxidation stability but not so good at lower temperatures.

Group III

These are derived from petroleum but are the most refined of the mineral oil basestocks. They are not chemically engineered like synthetics but offer the highest level of performance of all the petroleum basestocks. They are also known as “hydrocracked” or “molecularly modified” basestocks.
They are usually labelled/marketed as synthetic or semi-synthetic oils and make up a very high percentage of the oils retailed today.

Group IV

These are polyalphaolefins known as PAO and are chemically manufactured rather than being dug out of the ground. These basestocks have excellent stability in both hot and cold temperatures and give superior protection due to their uniform molecules.

Group V

These special basestocks are also chemically engineered but are not PAO.
The main types used in automotive oils are diesters and polyolesters. Like the group IV basestocks they have uniform molecules and give superior performance and protection over petroleum basestocks. These special stocks are used in all aviation engines due to their stability and durability. Esters are also polar (electro statically attracted to metal surfaces) which has great benefits. They are usually blended with Group IV stocks rather than being used exclusively.

It is common practice for oil companies to blend different basestocks to achieve a certain specification, performance or cost. The blending of group IV and V produces lubricants with the best overall performance which cannot be matched by any of the petroleum basestock groups.

True synthetics are out there though.

Here are some examples based on the products that I know and have the information on:

Mobil1 (pao)
Silkolene PRO (pao/ester)
Motul 300V (pao/ester)
Motul 8100 (pao)
Fuchs Titan Supersyn (pao)
Amsoil (pao)
Redline (pao/ester)
Shell Helix Ultra (pao)

You'll find tech data sheets on some of these products here: http://www.opieoils.co.uk/lubricants.htm

Hope this helps.

Simon
 

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My personal choice, knowing that all previous main SAAB dealers (in Bristol and Cardiff) also used this oil(!!) in my car (i.e. all it's life) is Mobile1.

DON'T buy 4 + 1 litre, and all the fuss of doing it yourself for £40 + filter.

Go to 'Kwik Fit' or 'Tyre Savers', specify their Mobile 1 option, and pay £40 for everything including the filter and labour!

Unless someone is trashing a car in racing conditions, there is little point in paying for premium oil (e.g. Mobile 1) and changing it every 6k miles every 2 months. A semi-synthetic will not sufficiently degrade to make any difference, and you will end up saving approx £100 per year.
 

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Originally posted by Paul D:
[qb]A semi-synthetic will not sufficiently degrade to make any difference, and you will end up saving approx £100 per year. [/qb][/b]
The risk with turbo-charged Saab engines is not the general degradation in the normal sense, but high temperature carburisation in the turbocharger bearings. This is the main reason why only full synthetics should be used.
 

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Originally posted by Mark B:
[qb] QUOTE
Originally posted by Paul D:
[qb] A semi-synthetic will not sufficiently degrade to make any difference, and you will end up saving approx £100 per year. [/qb][/b]
The risk with turbo-charged Saab engines is not the general degradation in the normal sense, but high temperature carburisation in the turbocharger bearings. This is the main reason why only full synthetics should be used. [/qb][/b][/quote]I'm with Mark on this one. Longer service intervals and Dealers/fleets using semi-synthetics in order to keep servicing costs down is now coming home to roost. Too many stories of failed turbos on the 9-5s may be an example of this.
 

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A semi-synthetic (hydrocracked) oil will degrade from the minute it's put in the engine due to the VI Improvers shearing, causing the oil to lose viscosity.

Synthetics are more thermally stable and contain little or no VI Improvers to work as a multigrade and therefore are more shear stable.

Here's the technical stuff.

Viscosity Index Improvers.

An oils viscosity will decrease as the engine temperature rises. Viscosity Index Improvers are added to reduce this thinning. They are a key addative in the production of multigrade oils.

VI Improvers are heat sensitive long chain, high molecular weight polymers that increase the relative viscosity of the oil at high temperatures. They work like springs, coiled at low temperatures and uncoiling at high temperatures. This makes the molecules larger (at high temps) which increases internal resistance within the thinning oil. They in effect "fight back" against the viscosity loss in the oil.

"Shearing"

The long chain molecules in VI Improvers are prone to "shearing" with use which reduces their ability to prevent the oil from losing viscosity. This "shearing" occurs when shear stress ruptures the long chain molecules and converts them to shorter, lower weight molecules. The shorter, lower weight molecules offer less resistance to flow and their ability to maintain viscosity is reduced.

This shearing not only reduces the viscosity of the oil but can cause piston ring sticking (due to deposits), increased oil consumption and increased engine wear.

Like basestock quality, VI Improvers also vary in quality. The best quality ones are normally found in synthetic oils (Group IV - PAO / Group V - Esters) and it is important to understand that the less of these in the oil the better the oil will stay in grade.

Which oils require more VI Improvers?

There are two scenarios where large amounts of these polymers are required as a rule.

Firstly in "wide viscosity" multigrades. By this I mean that the difference between the lower "W" number and the higher number is large for example 5w-50 (diff 45) and 10w-60 (diff 50) are what is termed as "wide viscosity" oils.

Narrow viscosity oils like 0w-30 (diff 30) or 5w-40 (diff 35) require far less VI Improvers and therefore are less prone to "shearing".

Secondly, mineral and hydrocracked (petroleum synthetic oils) require more VI Improvers than proper PAO/Ester (Group IV or V) synthetic oils as they are less thermally stable to begin with and this is due to the non-uniform molecules in petroleum oils as opposed to the uniformity of synthetics built in laboratories by chemists.

It is a fact that some synthetics require little or no VI Improvers to work as a multigrade due to their superior thermal stability.

Cheers
Simon
 

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Discussion Starter · #13 ·
This has proved to be a very informative thread. It makes good magazine reading! But I still wonder - is a GM branded Vauxhall 5/30 "fully shynthetic?" a good oil to use in road car with an LPT that isn't heavily thrashed?
 

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I've no doubt that this oil will suffice but we're talking entirely different animals here as the Vauxhall and Ford oils require low shear stability and are therefore hydrocracked petroleum oils labelled as synthetics.

The oils I mention are "proper" fully synthetics with no petroleum basestocks.

It's a bit like premiership vs 3rd division, there is no comparison. If you read the post I made quoting John Rowland of Silkolene this explains.

Cheers
Simon
 

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Mobil 'Delvac' is a large step up from Mobil 1, perhaps the basestock contains more Group 5 components, not sure.

Delvac is designed and used in USA by heavy turbo/diesel 18-wheelers. With much better oil filters they run 100,000 miles between changes in their very expensive engines.

Many turbo car users that drive hard use this oil. I have not seen it for sale in the UK, but due to the vast difference in the tax burden, it retails for approx GBP 5 per quart. Perhaps someone has seen it for sale here to the trucking industry?
 

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I agree all oils degrade, the moment they are put into an engine - it is the rate that is important, relative to the duration of use.

I don't think it is worthwhile paying the extra for a high grade fully synthetic if it is only being run 6k miles and changed every 2 months (unless vehicle being used in racing conditions).

With such a short change interval, I'd extend it to some 8k to 10k miles - which the likes of Mobile 1 can handle well within grade.

Alternatively, a good quality semi-sythetic will still be well within grade after 6k miles and 2 months running. I'm not aware of any semi-sythetics which are not speced for 'turbochargers'.

Also worth noting that Saab spec does not stipulate 'fully sythetic' for the 9000. And lets not forget, the specified service interval is 12k miles - changing oil at 6k with a semi sythetic is well within the Saab manufacturers limit and spec.
 

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Originally posted by Paul D:
[qb]I agree all oils degrade, the moment they are put into an engine - it is the rate that is important, relative to the duration of use. [/qb][/b]
That's only part of it. The other element is the extreme temps that the oil can be subject to around the turbo shaft, leading to the possibility of breakdown and carbonisation/damage. This occurs regardless of oil age and in all cases the true synthetics are more resistant to this.
 

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Of course.. the extreme temps are a direct contributant to the rate of degradation! I think you are stating the same thing.

But are you actually saying that good quality semi synthetic is not capable of suitably prolonging engine life, if run moderately at 6k intervals and 2 monthly changes in a Saab 9000 turbo, or are we all agreed on this?
 

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The point that's being missed here is a "good" (not cheap) semi-synthetic actually costs the same when you compare it's cost/life against a good fully synthetic.

Fully is around about twice the price but lasts at least twice as long so all things being equal the synthetic (with it's superior lubrication) is in fact better value for money.

Oil companies want you to buy the semi-synthetic and change it more often as they sell more oil!

Cheers
Simon
 

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That sounds like the definitive statement Oilmansi - but what about the oft-repeated advice to change oil and filter at least annually? On low-mileage cars (say 3000 pa) there's no way that an owner can benefit from the extended usage life of a fully synthetic. So what's the advice for us poor souls?
 
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