How To Know The Suitable Engine Oil For Your Car

When we go shopping for Engine Oil, a times you get confused because these products are branded with some codes that looks so confusing. Well, these codes are the Engine Oil Grade codes meant to help you recognize the particular engine oil suitable for your car. In this article we shall discuss how we can use those codes and labels to know the following which will help us pick the right engine oil for us.

• The purpose for which it is intended

• The viscosity

• The specifications that it meets

• The OEM Approvals that it carries and the codes

We shall also talk about some marketing blurb on the label you should ignore - in many cases they are meaningless as we shall explain later.

The Purpose

All oils are intended for a specific application and are generally are not interchangeable. You would not for example put an Automatic Transmission Oil or a Gear Oil in your engine! It's important to know what the oil's intended purpose is. So first thing to check is what type of oil is this.

The Viscosity

The viscosity of the Engine oil can be shown in either of two ways. They are
SAE J300 and its likes - This means it is a single grade engine oil or
10w-40 and the likes - This means it is a multigraded engine oil

Single-grade engine oil - as defined by SAE J300, cannot use a polymeric Viscosity Index Improver (also referred to as Viscosity Modifier) additive. SAE J300 has established eleven viscosity grades, of which six are considered Winter-grades and given a W designation.

The 11 viscosity grades are 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50, and 60. These numbers are often referred to as the "weight" of a motor oil, and single-grade motor oils are often called "straight-weight" oils.

Multi-graded engine oil - Most oils on the shelves today are "Multigrades", which simply means that the oil falls into 2 viscosity grades. 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 which is just too stressful.

The temperature range the engine oil is exposed to in most vehicles can be wide, ranging from cold temperatures in the winter before the vehicle is started up, to hot operating temperatures when the vehicle is fully warmed up in hot summer weather. A specific oil will have high viscosity when cold and a lower viscosity at the engine's operating temperature.The idea is to cause the multi-grade oil to have the viscosity of the base grade when cold and the viscosity of the second grade when hot.

For Example, If the Engine oil is graded 10w-40,

• 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 at low temperature. The lower the "W" number the better the oil's cold temperature/cold start performance.

• The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100°C. 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°C etc. Your car handbook will specify whether a 30, 40 or 50 etc is required for your car.

Therefore, an oil labeled as 10W-40 must pass the SAE J300 viscosity grade requirement for both 10W and 40, and all limitations placed on these viscosity grades. So it can be grades as 10W and also as 40.

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 Europeens d'Automobiles)

All good oils should contain both of these, and an understanding of what they mean is important.

• API Specification

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 Specifications

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

Approvals

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.

Ratings Or Labels That Are Of No Meaning

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

 We acknowledge the resources from Driverstechnology.co.uk that made this article possible.