Oil Specification & viscosity Info. - Webmaster

At the request of one of the forum members in the thread National Oil Change?, the following information on oil specification has been provided by "oilman"

Oil Specification

API Specifications
  • API = American Petroleum Institute
  • S = Service – Petrol Engine Performance
  • C = Commercial – Diesel Engine Performance
  • 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.
  • SN – Introduced in October 2010 for 2011 and older vehicles, designed to provide improved high temperature deposit protection for pistons and turbochargers, more stringent sludge control, improved fuel economy, enhanced emission control system compatibility, seal compatibility, and protection of engines operating on ethanol-containing fuels up to E85.
  • 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
  • CF-4 – 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
  • CF-2 – Introduced 1994, defines effective control of cylinder deposits and ring face scuffing, intended for 2 stroke diesel engines
  • CG-4 – 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
  • CH-4 – 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 fuelsSG – Introduced 1989 has much more active dispersant to combat black sludge.
  • CI-4 – 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.
  • CJ-4 – Introduced in 2010 exhaust emission standards. These oils are formulated for use in all applications with diesel fuels ranging in sulphur content up to 500 ppm (0.05% by weight). However, the use if these oils with greater than 15 ppm (0.0015% by weight) sulphur fuel may impact exhaust after treatment system durability where particulate filters and other advanced after treatment systems are used. Optimum protection is provided for control of catalyst poisoning, particulate filter blocking, engine wear, piston deposits, low and high temperature stability, soot handling properties, oxidative thickening, foaming, and viscosity loss due to shear.
ACEA Specifications

ACEA (European Automobile Manufacturers Association) have a system of rating oils, which you will find on the container of almost every oil on the market. These are the current specifications, previously oils were given separate petrol and diesel ratings, but from November 2004 onwards, those have been combined (A still refers to Petrol and B to Diesel engines).

  • A1/B1 – Category for Fuel Economy engine oils with especially low High Temperature High Shear viscosity. HTHS of 2.6 to 3.5 mPas applies to XW-20, 2.9 to 3.5 mPas for all others. Corresponds to the old A1 and B1 specifications with some new engine tests.
  • A2/B2 – Basic requirements.Will be replaced by the GLOBAL DLD-1 specification.
  • A3/B3 – Category for high-performance and Fuel Economy engine oils. Exceeds ACEA A1/B1 with regard to Noack (evaporation losses), piston cleanliness and oxidation stability.Extended oil change intervals possible.
  • A3/B4 – Same as A3/B3 but also for direct injection diesel engines.
  • A5/B5 – Category for high-performance engine oils. For TDI engines with Fuel Economy Performance. In addition with lowered HTHS (2.9 to 3.5). Extended oil change intervals possible.
Low SAPS Diesel Engines

An additional category appears in these specifications in which sulphate ash, phosphorous and sulphur content (SAPS) is limited.

  • C1 – Largely based on the ACEA A5/B5. Strict limitation of SAPS content.Low HTHS viscosity of >2.9 mPas
  • C2 – Same as C1 but with somewhat higher SAPS content permissible (as with C3)
  • C3 – Same as C2 except for HTHS > 3.5 and without Fuel Economy performance
  • C4 – Same SAPS content as C3, HTHS viscosity as C1

Cheers Simon

Edited by Xileno on 06/04/2021 at 21:21

Oil Viscosity - Webmaster
More Excellent information from Oilman. Taken from the thread Oil Viscosity


Oil Viscosity

It's thicker when cold 10w instead of 5w (poorer cold start protection) and thicker when hot sae 40 instead of 30 (will withstand higher operating temps).

This may be of help:

What is this thing called viscosity?

It?s written on every can of oil and it?s the most important visible characteristic of an oil.
The viscosity of an oil tells you how it reacts in certain circumstances and how it performs as a lubricant.
When a oil is subjected to external forces, it resists flow due to internal molecular friction and viscosity is the measure of that internal friction. Viscosity is also commonly referred to as the measurement of the oils resistance to flow.

There are two methods of viewing an oils resistance to flow. Firstly there is Kinematic Viscosity which is expressed as units indicating the flow of volume over a period of time and this is measured in centistokes (cSt).
An oils viscosity can also be viewed by measured resistance. This is known as Apparent Viscosity and it is measured in centipoises (cP).

However in the real world an oils viscosity is also referred to in such terms as thin, light and low etc. This suggests that the oil flows or circulates more easily. Conversly, terms such as heavy and high etc suggest the fluid has a stronger resistance to flow.

The reason for viscosity being so important is because it is directly related to the oils load-carrying ability - The greater an oils viscosity, the greater the loads that it can withstand. (It must be added when new not over a period of time as all oils ?shear down? with use)

An oil must be capable of separating the moving parts in your engine at the operating temperature. On the basis that an oils viscosity is related to its load carrying ability, you could be fooled into thinking that ?thicker? oils are better at lubricating but, you?d be wrong in this assumption. The fact is that in the wrong application a high viscosity oil can be just as damaging as using a low viscosity oil.

The use of an oil that?s too ?thin? can cause metal-to-metal contact, poor sealing and
increased oil consumption and conversely, an oil that?s too ?thick? can cause increased
friction, reduced energy efficiency, higher operating temperatures, and poor cold starts in cold temperatures.

It is very important that you select the correct oil, not too ?light? or too ?heavy? and your Owners Handbook is a very good place to start as it lists the temperatures and options.

Oils thicken at low temperatures and thin as the temperature increases. The actual rate of change is indicated by their viscosity index (this number normally listed on the oils technical data sheet indicates the degree of change in viscosity of an oil within a temperature range, currently 40-100 degrees centigrade)

An oil with a high viscosity index, will normally behave similarly at these two temperatures but an oil with a low viscosity index will behave quite differently. It will become very fluid, thin and pour easily at high temperatures. A higher index is better!

Multi-grade oils are designed to perform at high and low temperatures by adding polymers to a base oil (5w,10w, 15w etc) which are heat sensitive and ?uncoil? to maintain the higher viscosity sae 30,40,50 etc. This means that the oil can be used ?all year round? rather than using different oils for summer and winter.

It is important to understand that the selection of the correct oil for your car is not just guesswork, you must consider the temperatures at which you need the oil to operate a 0w, 5w oil is better for cold starts as the oil circulates more easily when it?s cold and is able to flow around the engine more easily and quickly, offering protection at the
critical moments following cold engine start-up. These oils are also known to give better fuel economy and engine performance.

Finally, all oils ?shear? or thin down with use and this means that an oil that started life as a 10w-40 will with use become a 10w-20. The period of time this takes depends on the type and quality of the oil. The most ?shear stable? oils are proper Synthetics, either PAO (Poly Alph Olefins) or Esters which have very high thermal stability. They are in general of the more expensive variety but last longer and give the best levels of protection.



Also see Simon's latest contribution on the subject of oil HERE

And some more stuff:-
Gear Oil Questions and Answers
16 important OIL questions answered
What does 10w-40 mean..?

Edited by Dynamic Dave on 22/02/2008 at 13:40