Oil is a catch all word that describes the liquid that prevents your car from seizing up and allows it to do obscene amounts of miles between oil changes. It is also in your gearbox, power steering and the chance is that you also have some in the garage that is used for stopping the door hinges squeaking. But each oil is different, so a much better term is lubricant, and lubricants have come a long way.
A modern engine will run huge distances and put up with an enormous amount of abuse and still start every morning. This is due to the incredibly fine engineering tolerances that are the norm in today's cars, and the quality of the oil that maintains a film strength that prevent wear even when the clearances are truly microscopic.
It is absolutely essential that the correct oil is fitted into your car, and Castrol were correct when they described it as "liquid engineering". Indeed modern oil has additives that prevent sludge, combat acid build up, and on a molecular level coat vulnerable components. This is apart from getting the right viscosity, and choosing synthetic or mineral options.
We make sure that the oil we use is correct for every vehicle, we always ensure that our oil is top quality by checking it's specification, but this is your guide through the lubricant bog. So have a look at the following information, and you will never call it oil again
If a can of oil does not contain the following basic information then DO NOT buy it look for something that does!
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The purpose for which it is intended (i.e. Motor oil, Gear oil etc)
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The viscosity (i.e. 10w-40, 5w-30 etc for Motor oils and 80w-90, 75w-90, etc for Gear oils)
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The specifications that it meets (should contain both API and ACEA ratings)
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The OEM Approvals that it carries and the codes (i.e. MB229.3, VW503.00, BMW LL01 etc)
So, what does the above information mean and why is it important?
THE BASICS
All lubricants 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 intended purpose is.
VISCOSITY
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
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 Europeans d'Automobiles) all good oils should contain both of these and an understanding of what they mean is important.
API
This is the more basic as it is split (for passenger cars) into two categories. 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:
PETROL
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.
Note: 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.
DIESEL
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.
Note: 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
ACEA
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 categories 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 oils.
