Oil labelling explained - oilman
What?s written on your oil bottle and what does it mean.

This post may seem like going back to basics but I am constantly surprised by the amount of people who do not know or understand what is written on a bottle of oil and therefore no idea of what they are buying/using.

To be blunt about the subject, if a bottle of oil does not contain the following basic information then DO NOT buy it look for something that does!

1) The purpose for which it is intended (i.e. Motor oil, Gear oil etc)

2) The viscosity (i.e. 10w-40, 5w-30 etc for Motor oils and 80w-90, 75w-90 etc for Gear oils)

3) The specifications that it meets (should contain both API and ACEA ratings)

4) The OEM Approvals that it carries and the codes (i.e. MB229.3, VW503.00, BMW LL01 etc)

Ignore the marketing blurb on the label it is in many cases meaningless and I will explain later what statements you should treat this with some scepticism

So, what does the above information mean and why is it important?


All oils are intended for an application and in general are not interchangeable. You would not for example put an Automatic Transmission Oil or a Gear Oil in your engine! It is important to know what the oils intended purpose is.


Most oils on the shelves today are ?Multigrades?, which simply means that the oil falls into 2 viscosity grades (i.e. 10w-40 etc)

Multigrades were first developed some 50 years ago to avoid the old routine of using a thinner oil in winter and a thicker oil in summer.

In a 10w-40 for example the 10w bit (W = winter, not weight or watt or anything else for that matter) simply means that the oil must have a certain maximum viscosity/flow at low temperature. The lower the ?W? number the better the oils cold temperature/cold start performance.

The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100 degC. This is a fixed limit and all oils that end in 40 must achieve these limits. Once again the lower the number the thinner the oil, a 30 oil is thinner than a 40 oil at 100 degC etc. Your handbook will specify whether a 30, 40 or 50 etc is required.


Specifications are important as these indicate the performance of the oil and whether they have met or passed the latest tests or whether the formulation is effectively obsolete or out of date.
There are two specifications that you should look for on any oil bottle and these are API (American Petroleum Institute) and ACEA (Association des Constructeurs Europeens d?Automobiles) all good oils should contain both of these and an understanding of what they mean is important.


This is the more basic as it is split (for passenger cars) into two catagories. S = Petrol and C = Diesel, most oils carry both petrol (S) and diesel (C) specifications.

The following table shows how up to date the specifications the oil are:


SG - Introduced 1989 has much more active dispersant to combat black sludge.

SH - Introduced 1993 has same engine tests as SG, but includes phosphorus limit 0.12%, together with control of foam, volatility and shear stability.

SJ - Introduced 1996 has the same engine tests as SG/SH, but phosphorus limit 0.10% together with variation on volatility limits

SL - Introduced 2001, all new engine tests reflective of modern engine designs meeting current emissions standards

SM - Introduced November 2004, improved oxidation resistance, deposit protection and wear protection, also better low temperature performance over the life of the oil compared to previous categories.


All specifications prior to SL are now obsolete and although suitable for some older vehicles are more than 10 years old and do not provide the same level of performance or protection as the more up to date SL and SM specifications.


CD - Introduced 1955, international standard for turbo diesel engine oils for many years, uses single cylinder test engine only

CE - Introduced 1984, improved control of oil consumption, oil thickening, piston deposits and wear, uses additional multi cylinder test engines

CF4 - Introduced 1990, further improvements in control of oil consumption and piston deposits, uses low emission test engine

CF - Introduced 1994, modernised version of CD, reverts to single cylinder low emission test engine. Intended for certain indirect injection engines

CF2 - Introduced 1994, defines effective control of cylinder deposits and ring face scuffing, intended for 2 stroke diesel engines

CG4 - Introduced 1994, development of CF4 giving improved control of piston deposits, wear, oxidation stability and soot entrainment. Uses low sulphur diesel fuel in engine tests

CH4 - Introduced 1998, development of CG4, giving further improvements in control of soot related wear and piston deposits, uses more comprehensive engine test program to include low and high sulphur fuels

CI4 Introduced 2002, developed to meet 2004 emission standards, may be used where EGR ( exhaust gas recirculation ) systems are fitted and with fuel containing up to 0.5 % sulphur. May be used where API CD, CE, CF4, CG4 and CH4 oils are specified.


All specifications prior to CH4 are now obsolete and although suitable for some older vehicles are more than 10 years old and do not provide the same level of performance or protection as the more up to date CH4 & CI4 specifications.

If you want a better more up to date oil specification then look for SL, SM, CH4, CI4


This is the European equivalent of API (US) and is more specific in what the performance of the oil actually is. A = Petrol, B = Diesel and C = Catalyst compatible or low SAPS (Sulphated Ash, Phosphorus and Sulphur).

Unlike API the ACEA specs are split into performance/application catagories as follows:

A1 Fuel economy petrol
A2 Standard performance level (now obsolete)
A3 High performance and/or extended drain
A4 Reserved for future use in certain direct injection engines
A5 Combines A1 fuel economy with A3 performance

B1 Fuel economy diesel
B2 Standard performance level (now obsolete)
B3 High performance and/or extended drain
B4 For direct injection car diesel engines
B5 Combines B1 fuel economy with B3/B4 performance

C1-04 Petrol and Light duty Diesel engines, based on A5/B5-04 low SAPS, two way catalyst compatible.
C2-04 Petrol and light duty Diesel engines, based on A5/B5-04 mid SAPS, two way catalyst compatible.
C3-04 Petrol and light duty Diesel engines, based on A5/B5-04 mid SAPS, two way catalyst compatible, Higher performance levels due to higher HTHS.

Note: SAPS = Sulphated Ash, Phosphorous and Sulphur.

Put simply, A3/B3, A5/B5 and C3 oils are the better quality, stay in grade performance oils.


Many oils mention various OEM?s on the bottle, the most common in the UK being VW, MB or BMW but do not be misled into thinking that you are buying a top oil because of this.

Oil Companies send their oils to OEM?s for approval however some older specs are easily achieved and can be done so with the cheapest of mineral oils. Newer specifications are always more up to date and better quality/performance than the older ones.

Some of the older OEM specifications are listed here and depending on the performance level of your car are best ignored if you are looking for a quality high performance oil:

VW ? 500.00, 501.00 and 505.00

Later specs like 503, 504, 506 and 507 are better performing more up to date oils

MB ? 229.1

Later specs like 229.3 and 229.5 are better performing more up to date oils.

BMW ? LL98

Later specs like LL01 and LL04 are better performing more up to date oils.


Above is the most accurate guidance I can give without going into too much depth however there is one final piece of advice regarding the labelling.

Certain statements are made that are meaningless and just marketing blurb, here are a few to avoid!

Recommended for use where?????
May be used where the following specifications apply?????
Approved by?????????..(but with no qualification)
Recommended/Approved by (some famous person, these endorsements are paid for)
Racing/Track formula (but with no supporting evidence)

Also be wary of statements like ?synthetic blend? if you are looking for a fully synthetic oil as this will merely be a semi-synthetic.

Like everything in life, you get what you pay for and the cheaper the oil the cheaper the ingredients and lower the performance levels.

If you want further advice then please feel free to ask here or contact us through our website at www.opieoils.co.uk.

Oil labelling explained - kithmo
I understand the low temperature bit, but If a manufacturer gives a range of viscosities, e.g. 5W/30, 5W/40 or 10W/40, what are the advantages of say using the 5W/40 over the 5W/30 and vice versa ? Am I right in thinking a hot 40 gives better protection than 30 when hot, but not so good economy ?
Oil labelling explained - robcars
Pretty good summary of oil information.

The only comment I feel is needed is that all oils recommended by the vehicle assembler are for a new low mileage engine. As wear increases, the viscosity and type of oil may need to be changed and as such advice should be sought from people with knowledge such as the op.

In general answer to kith, the higher the viscosity number, within reason, then the better the engine protection, but more drag, so affecting economy. All oils are a compromise, and driving style, mileage, journey type, oil change frequency etc all affect the ideal choice for any engine.

There is no substitute for regular oil changes, and I would always put engine protection in preference to economy, but others may disagree.
Oil labelling explained - nortones2
Any factual information to back up this idea of a sliding scale of oil? Odd that no manufacturer or oil maker states this SFAIK. The 505.01 for example for VW PD is replaced by which oil as it ages?

Oilman: Its too complicated already but you might usefully clarify that API Cx grades are only intended for diesel trucks. API have no passenger car diesel engine test method. They don't do diesel cars:) However, ACEA have an E series for HGV, in addition to the A, B and C headers. BTW, European manufacturers usually adopt a more stringent OEM requirement, which should (must in many cases) take precedence over both ACEA and API.
Oil labelling explained - oilman
With regards to VW specs, the new ones are VW504.00 and 507.00.

Many new oils carry both but for reference VW504.00 relates to petrol and 507.00 to diesel including PD engines.


Oil labelling explained - oilman
To expand upon what I have already said above, this hopefully answers you.

If you see an expression such as 10W-40, the oil is a multigrade.

This simply means that the oil falls into 2 viscosity grades, in this case 10W & 40.

This is made possible by the inclusion of a polymer, a component which slows down the rate of thinning as the oil warms up and slows down the rate of thickening as the oil cools down.

It was first developed some 50 years ago to avoid the routine of using a thinner oil in winter and a thicker oil in summer.

For a 10w-40 to attain the specification target a 10W ( W = winter) the oil must have a certain maximum viscosity at low temperature. The actual viscosity and the temperature vary with the viscosity grade but in all cases the lower the number, the thinner the oil, e.g. a 5W oil is thinner than a 10W oil at temperatures encountered in UK winter conditions.

This is important because a thinner oil will circulate faster on cold start, affording better engine protection.

For a 10w-40 to attain the other specification target a 40 oil must fall within certain limits at 100 degC. In this case the temperature target does not vary with the viscosity grade, if there is no "W", the measuring temperature is always 100degC. Again the lower the number the thinner the oil, a 30 oil is thinner than a 40 oil at 100 degC., which is typical of maximum bulk oil temperatures in an operating engine.

The engine makers are, of course, very well aware of this and specify oils according to engine design features, oil pump capacities, manufacturing tolerances, ambient temperature conditions etc. It is important to follow these guidelines, they are important and are an are stipulated for good reasons.

If the engine has been modified, the operating conditions may well be outside the original design envelope. The stress on the oil caused by increased maximum revs, power output and temperature may indicate that oil of a different type and viscosity grade would be beneficial.


Oil labelling explained - Sprice
Thanks oilman, a very useful post!
Oil labelling explained - Chris S
I put 10w30 instead of 10w40 in my old Metro. A month or two later the head cracked. Could this have been a contributing factor?
Oil labelling explained - Roger Jones
Being no technical expert, I hesitate before adding anything to the wealth of information above, but I do find it helpful to hang on to the fact that the thicker oils -- thicker when hot, thicker when cold -- tend to be recommended for very high-perfomance engines being pushed hard in hot environments. So, when faced with a 50 or higher I think of superbikes and Ferraris being raced in the Middle East, and in those cases the lower numbers are usually higher too (15W, 20W).

Another simplistic view is that 10W-40 can be regarded as normal for UK use (with the singular exception of 5W-30 for Ford Zetec engines), although 5W-40 or 0W-40 will give better cold-engine protection.

Finally, some would say that cold-engine protection is the most important issue of all, as 80% and more of engine wear occurs at cold start-up. Hence the appeal of 0W-40 Mobil 1.
Oil labelling explained - jc2
Ford drivers'manuals used to have a good chart showing what oil was recommended for extremes of temperature,both up and down.
Oil labelling explained - cheddar
Ford drivers'manuals used to have a good chart showing what oil
was recommended for extremes of temperature,both up and down.

As does my Honda mower, I was using straight 30 mineral oil so I could only cut the grass at ambient temperatures between 5degC and 35degC however I now use 10W-40 semi synth (same as the wife's Clio and my Kawasaki) so I can now tend to the lawns between -10degC and 50degC. Most useful :)
Oil labelling explained - cheddar
Another simplistic view is that 10W-40 can be regarded as normal
for UK use (with the singular exception of 5W-30 for Ford
Zetec engines), >>

Not just Zetec rather all modern Ford engines, Duratec, Durtorque etc. IIRC the only exception is the VAG PD diesel in the now discontinued Galaxy.
Oil labelling explained - Roger Jones
Thanks, Cheddar.

I think I found somewhere that "Zetec" has no technical meaning, but is simply a marketing label. Does that go for the other Ford variants too?
Oil labelling explained - jc2
They were going to call all engines "Zeta" but Lancia had the name registered.
Oil labelling explained - Sherwood
Can you help?
I own a 1998 BMW 318 TDS Touring E36 40000 miles
For the past number years I have given the car an oil change every 6-9 months in between main servicing using Mobil 1 Semi-synthetic at Kwik-fit.when I took it in to-day Kwik- fit said that according to their computer BMW have sent out a directive saying that Mobil 1 is not recommended for my car.
Have you heard of this? My independant BMW garage who services my car hasn't. I am now confused. Obviously the new recommended oil is twice the price.
Oil labelling explained - injection doc
Hi Sherwood. I would recommend you ring up Mobil technical as they are very helpfull & I hate to admit it but Kwik-Fit could be right. My wife had a 1.4hdi peugeot 206 & that also stated in the handbook not to use Mobil 1 & mobil technical aggreed. It was to do with the addatives in the oil & Aromatic hydrocarbons & the reaction. I think Mobil have now developed a 0-30 economey oil for diesels but worth a check.
I have to say when I contacted a Peugeot dealer they new nothing of it & I checked with others & they all said the same, but it was clear in the handbook! so a dealer doesn't always know everything. The dealers advice was to stick to what the hand book says
Oil labelling explained - Roberson
Very interesting and useful information Simon. Perhaps more so for me, because I rely solely on the label to tell me whether its suitable for me or not. I usually chose by selecting those of suitable viscosity and VAG approval and that?s the job done, ignoring API and ACEA markings. Maybe I should pay greater attention to these after all.

It appears that even the manufacturers can't label their products properly. My garage (VW specialist) filled my old Polo with Magnatec 10-40. Not quite sure this was the right choice I looked at the label on the 1ltr bottles and its marked to VW505.00 and VW500.00. The latter approval is the one I wanted, so thought nothing more of it. However, the same 4.5ltr bottle and the Castrol website actually only give VW505.00 approval (which is a diesel oil according to VW handbooks).

This much maligned Magnatec is of SL/A3/B3 type, so maybe not a bad choice after all. But I?m still not 100% happy because of the lack of VW approval, so may fill with 'Quantum Synta Silver' next time.
Oil labelling explained - Dalglish
My garage (VW specialist) filled my old Polo with Magnatec 10-40.


roberson - you do not say exactly which model polo you have. check the castrol magnatec spec for you polo here:


Oil labelling explained - Roberson
1993 1.0i

Magnatec is what Castrol recommend, but so many people dislike it. Quantum however is highly recommended by some and I?m lead to believe its VAG's own brand, although I can't recall seeing any API/ACEA markings on the can I looked at in the VW dealer.

This might be of use to some people: tinyurl.com/zh9ys

Oil labelling explained - davidomegadriver
I have a Vauxhall Omega petrol X reg with 120K on the clock, still going strong. My brilliant local garageman is happy to change the oil to one which would suit my car best, because I've been advised to oilchange more often from now on. What oil change interval do you suggest, and what specification of oil. Many thanks. He's happy to order to your spec.
Oil labelling explained - AdyBeee
My owners manual recommends SAE 5W-30 oil for my Ford Duratech ST200 engine. Obviously, the manual states that Ford oil should be used.

The oil change interval is 10000 miles, however, I change the oil myself every 5000 miles with Halfords SAE 5W-30 inbetween the Ford services. The reason I do this is because, as previously stated, all oils loose their shear strength.
Where I differ from the common opinion is that no matter the cost of the oil, it will shear just as quickly as the cheaper versions. I have been advised that to change the oil more often with the correct grade is better than to change at the recomended interval using the expensive brands.
This, molecular structure, advise comes from a college tutor with more materials degree's than I have GCSE's.

Oil labelling explained - Dynamic Dave
I have a Vauxhall Omega petrol X reg

Stick with the recommended oil change intervals, and use Vauxhalls "own brand" 10w/40 semi synth oil.
Oil labelling explained - mgbv8
Shear stability refers to an oil's ability to resist shear and to regroup if some molecules do shear.

Oils which have a high probability of "regrouping" and resisting molecular shearing are considered "shear stable;" while those suffering permanent shear are not shear stable.

Mineral oils tend to shear with a large percentage of molecules not "regrouping."

The majority of PAO and ester molecules tend to "regroup" after shearing and to resist shear much better, thus are considered more shear stable than mineral oils.

The reason is that synthetic oils have narrow molecular species and sizes that tend to stay together better (better molecular bonding), while mineral oils have a huge mix of molecules of different sizes and bonding forces which may shear permanently.

Viscosity improvers are not shear stable and PAO and ester oils use few viscosity improvers and in some cases none, wheras mineral oils can only make the multigrade specification by using these additives.
Oil labelling explained - obbig
Sorry if this is obvious to everyone else, but what exactly is the difference in engine oil between "petrol" oil and "diesel" oil? Surely they all do exactly the same job? Is it going to hurt my diesel engine if I top it up with a bit of "petrol" oil, or vice versa?
regards obbig
Oil labelling explained - prm72
Most oils now cater for petrol and diesel eg: A3/B3 printed on the can and is fine for either. In fact i was told this is better for my diesel than just a B3 or B4 because it has better lubrication for the top end of the engine ( dont know how true that is ).
Oil labelling explained - oilrag
"The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100 degC. This is a fixed limit and all oils that end in 40 must achieve these limits."

The `limits` are different though for grades ending in `40` , for example 5w40 oil is allowed to be thinner at 100c compared with 15w40.

I always thought this was rather weasely,as you would assume all oils ending in `40` would be the same viscosity at 100c.
Oil labelling explained - kestrel
I've been told Fords own Oil is Havoline.Morrisons are selling Havoline 5/30 fully synthetic to Ford's spec, can this be used in place of semi-synthetic.
Oil labelling explained - chrise17
A 5w30 is also recommended for the vauxhall cars now or at least most of the post 2001 models.
Is a 5w30 adequate protection at the normal operating tempature of an engine or is it a manufacturers compromise to squeeze as much mpg as possible?
If so I would rather use a 5w40.
As an engine ages I assume wear & tear takes it toll so a w40 oil would offer greater protection but when is the best time to use it and if a w40 oil is used from the off where a w30 was originally recommended would this not contribute to the wear & tear as the spaces between moving parts is so small so the thicker oil would cause greater friction than a w30?
Oil labelling explained - Ruperts Trooper
The W goes with the first rating to indicate it's "Winter" viscosity, ie when the engine's cold.

-30 oil will give less drag, therefore better economy, than -40, but unless you're an engine designer or a petrochemical expert you're best taking the recommendation of the vehicle manufacturer.
Oil labelling explained - JustMike

Thankyou Simon for sheddding some light on a subject which seems intentionally complicated by the marketing men. I look after my daughters Passat TDI which has done 120k in its 7 year life, very successfully - so far. I change the oil and filter at 5 -6k intervals and use a 10-40 semi synthetic - preferring that to a dearer full synthetic left for perhaps twice the miles. My son in law says I am still in a gas light era as he does 20k between changes in his Audi with the same 1896cc VW engine as the Passat but has an approved (?) fully synthetic oil put in. I dont think its coincidence that such long periods between changes seems to result in many engine /turbo problems at 100k unlike the 120K we have achieved so far. Am I on the right lines or am I a dinosaur ? Thanks again. Mike

Oil labelling explained - Brit_in_Germany

Perhaps it is time for the "sticky" to be updated? It does not refer to ACEA C specification oils and these are becoming standard for diesels with DPFs. Simon's post at the start of the thread does include these.

On an aside, does anyone know why C1 oils are so rare? The approved oil for Jaguar XF diesels is a derivaton of the ACEA C1 specification but only one or two manufacturers seem to sell suitable oil, either C1 or Jag spec.


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