"Full" Synthetic vs. "Semi" Synthetic

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So if marketed "Full" Synthetic engine oils are not a base stock man made synthetic, then what is the difference vs. a "Semi" Synthetic?
I understand there may be different levels of additives between the two, but what really gives?

What is the point of a semi?
 
"Semi" uses Group I or II basestocks together with Group III, "Full" uses Group III.

Semi uses the group III to reach a performance level not possible on full dino Group I or Group II.
 
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Semi synthetics are generally mixes of Group II Mineral and Group III synthetics to achieve better performance where a mineral oil might not be up to the job, so generally most semi synthetics are only marginally better than Group II Mineral oils,some have 15% Synthetic, others are in the single digits from what i've learnt
 
Originally Posted By: wemay
A good read...

http://machinerylubrication.com/Read/533/base-oil-trends

Quote:
Lubrication performance that previously was achieved only in small-volume niche applications, using PAO and other specialty stocks, is now widely available using the new generation of Group II and Group III oils.


Just because an oil uses a US standard full synthetic base stock (A hydrocrack synthetic or group 3) does not mean it is a good oil. The additives are in many ways more important than the actual base stock.

At present there is a glut of cheap HC synthetic base stocks available, so some new oil mixers are advertising so called full synthetics that lack the all important additives and perform worse than some good major brand conventional oils.
The situation is much better if you look at oils with German standard (Group 4) full synthetic or GTL (Gas To Liquids) technology base stocks, as only the more major oil companies manufacture such oils and they don't seem to skimp on the additives.
 
With a "semi synthetic" the spec's should be considered because the percentage of synthetic oil will never be known for sure by the consumer.

A local municipality here uses Motorcraft semi synthetic engine oil with excellent results in both police and other vehicles.
 
I never liked semi or para synthetic because one usually did not know what percentage really was synthetic and if it then was worth the extra expense. I pretty much only use synthetic anymore.
 
Just go to buy a jug of dino and a jug of full synthec and mix them yourself. It's cheaper and you know for sure the percentage of mixing.
 
There are a lot of oils who still have meaningful % of PAO and Esters. For example, Castrol 0W40 that you can get in Wal Mart has more then 50% of PAO. Mobil1 5W30 ESP for diesels is VISOM based, meaning it is HC based, but looking at numbers it has meaningful % of both PAO and Esters.
In the end, what matters are achieved numbers and used oil analysis. For example old Mobil1 0W40 was VISOM, so HC oil. But considering 8.7% NOACK, HTHS of 3.8cp etc. it is hard to argue that it was not one of the best high performance oils on the market.
As for semi-syntehtics, I do not want even to look at that on the shelf for modern cars.
 
In the good old days when there were just Group Is, Group IIIs and PAOs, full minerals were 15Wxx and 20Wxx, semi's were Group I/III 10Wxx (except in the US where high Noack all-mineral 10W30's were the norm), full (or very rich) synthetics were 5Wxx and anything that was 0Wxx was mainly PAO based. It worked this way because for each successive reduction in W number, you need better, higher saturates base stock to make the appropriate CCS spec (or in Europe, the Noack spec). Minerals were cheap and nasty, full synthetics were good but expensive and semi's were somewhere in between.

Then along came Group II base oils especially in the US where they totally pushed out Group I. Now 20Wxx, 15Wxx, 10Wxx and 5Wxx could be made with Group II (with a bit of Group II+ for 5Wxx). These oils are pretty good in terms of their stability and sludge performance but tend to have high Noack (especially the 5Wxx oils). You can get full and semi synthetic 5Wxx oils and their primary advantage is lower Noack. They are a bit better than full Group II 5Wxx oils in terms of stability, etc but the performsnce gap is far, far smaller than in the days of Group I & Group III oils.

In terms of additives, things are very much of a muchness. Because if the way the specs are written, it's quite realistic to have one additive package at one single treat rate in all oils, be they full mineral, semi or full synthetic. Often there's a overlay of something extra for reasons of differentiation but the core can be fixed.
 
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Originally Posted By: Toaster_Jer
I never liked semi or para synthetic because one usually did not know what percentage really was synthetic and if it then was worth the extra expense. I pretty much only use synthetic anymore.

My view is pretty basic. If we can't trust what the oil company is doing with the oil, then it might be time to buy from a different company. Personally, I've never seen a need for a synthetic blend, unless it happened to be the answer to another problem. Already mentioned in the thread are formulation goals. Specification goals could go with that, too, given that one could get dexos1 as a blend. Also, when I had a desire for high mileage oils for the leaking F-150, that got me a synthetic blend pretty much by default.
 
In North America where full synthetics are plentiful and cheap, I can see how most people would ignore the semi-synthetics and jump straight to full synthetics.

In Australia the price jump between mineral and semi-synthetic and then full synthetic is significant. Let's say an extra $20 per level up. Suddenly semi-synthetics make sense. They are the least expensive oils that make decent specs like A3/B4 or Dexos1 and at the same time save you some real coin.

I'm also fortunate to live in a warm climate, so no need for 0W or 5W oils where synthetics really shine. A 10W or 15W is plenty of cold start for me, and here minerals work well and have less volatility issues.

I've run plenty of Valvoline DuraBlend 10W-40 and now I'm running Castrol Magnatec 10W-30. Both are semi-synthetics rated API SN and ACEA A3/B4. I've never felt at a disadvantage running this type of semi-synthetic or synblend for regular applications. If I was racing or living in a very cold climate, then I would probably feel a little different.

Australia also doesn't have many "silly" oils. If you see a 5W40 or a 0W40 then it is a full synthetic. A 10W40 will be most likely a semi-synthetic and a 40 grade mineral oil will always be a 15W40. No 10W40 minerals here, similarly I don't recall ever seeing a mineral 5W30. Just about every 5W30 I see is a full synthetic. The blends and the minerals are all 10W30.
 
Just another comment on semi's...

Back in the days of A3/B3, when B3 used the VW 1431 engine test, you used to see semi-synthetic 10W40's with as little as 10 to 20% Group III content. It was just enough to get the viscometrics and Noack on-grade. This changed a lot when B3 and B4 moved to using the more severe VW TDi test. Now it's common to see B4 oils containing more Group III than Group I. Speaking personally, I might give oils claiming 'synthetic technology' or similar weasel words a wide berth. The wording implies 'mainly synthetic' and this isn't always the case.
 
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SofJoe, how many of these name brand semi-synthetics would contain Group 1 ?

I always assumed that if most SN mineral oils are pretty close to pure Group 2, and synthetics are all Group 3 ( or above), then a semi-synthetic would be a Group 2 and Group 3 mix.

Is Group 1 content just to save on costs or does it confer some technical feature that is desired ?

Where is the break-even point between a pure Group 2 and a Group 1+ Group 3 blend ?
 
I agree - too many "who dats" with synthetic on the label for me to follow - so I just stick with one of the majors that often do another type of semi: they use some of the other high end base fluids added with the GrIII - IMO the intent is to reach decent performance standards while keeping us in $22 Walmart jugs (still seek Dexos badge, GF5, API, etc)
It is easier to achieve this when you produce the various base oils to start with.
(MolaKule has commented on the use of 2 or 3 synthetic base fluids)
 
Originally Posted By: SR5
SofJoe, how many of these name brand semi-synthetics would contain Group 1 ?

I always assumed that if most SN mineral oils are pretty close to pure Group 2, and synthetics are all Group 3 ( or above), then a semi-synthetic would be a Group 2 and Group 3 mix.

Is Group 1 content just to save on costs or does it confer some technical feature that is desired ?

Where is the break-even point between a pure Group 2 and a Group 1+ Group 3 blend ?



The answer to the question depends on where you are in the world. Group I is still widely used in Europe so here you still see Group I/III semi's. In your neck of the woods, Asia and the US, Group II has largely displaced Group I in engine oils so yours will be Group II/III mixes.

The refining process for making Group IIs is far more efficient than the old solvent extraction process used for making Group Is. This means that Group IIs are usually cheaper than Group I's so using Group I is often supply availability driven rather than cost driven.

Group II oils are strange in that they have oxidative stability properties close to those of Group III oils but have viscometric and volatility properties that are closer to Group I base oils. What this means is that a Group II based semi 10W40 may need just as much Group III to be on-grade as one based on Group I. Also you could well find that the Group II/III oil needs to contain more antioxidant than the Group I/III oil even though it's inherently more oxidatively stable!
 
Thanks SonofJoe.

I've never had an issue with my name brand semi-synthetics. But I like to think I'm buying a bit more, over a conventional oil, but I worry that I may be falling for a marketing gimmick.

I was speaking to Valvoline Australia over the phone recently. The tech said their semi-synthetic DuraBlend contains larger amounts of synthetic base (about 30% I've heard from various other sources), but their synthetic blend EngineArmour contains less synthetic base and I was advised to consider it similar to a conventional oil for deciding on oil change intervals.

It seems Valvoline define semi-synthetic to be a high synthetic content and synthetic blend to be code words for a low synthetic content. I've always preferred the DuraBlend for this reason, but it has priced itself out of the market, as another $5 gets you full synthetic Edge or SynPower.

I also worry about Group 1 content in the EngineArmour, but that's just a gut feeling based on no real facts. Still I buy DuraBlend or Magnatec if I want a semi-syn, but never EngineArmour which is more a mineral oil with a touch of syn for advertising.
 
Originally Posted By: SR5


I also worry about Group 1 content in the EngineArmour, but that's just a gut feeling based on no real facts. Still I buy DuraBlend or Magnatec if I want a semi-syn, but never EngineArmour which is more a mineral oil with a touch of syn for advertising.


Valvoline use the term Synthetic technology to describe Engine Armour. Synthetic technology seems to be the new mineral/conventional.
 
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