What's new

All you wanted to know about engine oils & fuels !

Grayedout

Members
Messages
456
Reaction score
82
Location
Derbyshire
Car
2004 Accord 2.2
Here is the start of my post. I'll come back and add bits as I get time!

What makes up an oil?
A modern oil is made up of two major parts: Basestock and Additives in a large range of percentages from 99% Basestock / 1% Additives to 75% Basestock / 25% Additives

Basestock - this comes in two variations: Mineral & Synthetic and is classed into 5 different groups with the two lowest being Mineral and the remaining three being Synthetic.

Mineral Basestock – This is what comes out of the ground and is then refined to produce all the products that we use from it such as engine oil, fuel, and everything else. Dependent on where in the world the oil is sourced (North Sea, Middle East etc.) and how much it has been refined then the Basestocks have different properties and indeed different qualities and so these are split into two classes (I & II) with I being the lowest quality and hence cheapest. BUT even when the oil has been refined then it is not fully suitable for protecting a modern engine and has a lot of shortfalls hence why we require Additives! (more later)

Synthetic Basestocks – These Basestocks are produced ‘in the lab’ rather than being straight out of the ground and the benefit of this is some of the shortfalls of the Mineral Basestocks can be designed out and some of the properties that are required for modern engines can be built into the Basestocks which will then require less additives. Synthetic Basestocks are split into three classes (III, IV, & V) with the quality (and hence cost) increasing with class number.

‘Synthetic’ – A quick word to say that Synthetic is not always Synthetic !!! Due to a court case in America several years ago it was argued successfully that a Mineral Oil that had been hydrocracked (more extensive refining as far as I know) can actually be classed as Synthetic. Therefore, a Synthetic oil can actually be a hydrocracked Mineral oil! Believe me it’s a minefield !
 

Grayedout

Members
Messages
456
Reaction score
82
Location
Derbyshire
Car
2004 Accord 2.2
Can't see how to edit the above post to add more so will have to put it here.

Lubrication Theory
Before I go any further then a quick bit of lubrication Theory which will help with some of the later items!

The friction between two moving surfaces separated by a lubricant is classified by something called the Stribeck Curve which splits the interaction between the surfaces into three areas:

Hydrodynamic – in relative ‘low’ pressure areas such as main and big end bearings then the metal surfaces are kept apart by a full fluid film and in this area the viscosity of the oil has a major influence

Mixed – as the pressures increase then a mix of hydrodynamic and boundary lubrication takes place

Boundary – in high pressure areas such as between cam and followers and between rings and the cylinder wall then all of the oil fluid gets squeezed out and the protection is provided by the additives alone which form protective films on the surfaces to support the loads


Additives
Will now start talking about some of the many additives that make up a modern oil and the effect that they have.

Viscosity
Firstly, the fluid property that most people know about, or think they know about is viscosity.

Modern oils are called multigrade and are classified by two numbers which classify their low temperature and high temperature viscosity. The low temperature figure is not actually calculated by measuring the viscosity but by running a test which measures the lowest temperature at which the oil can still be pumped. This classifies each oil into a range which is given a number 0, 5, 10W etc. The ‘W’ means Winter. The second number is the actual viscosity of the oil at 100°C and again this is denoted by a number which classifies the range that the viscosity in in. For example, a 30 grade oil has a viscosity at 100° between 9.3 and 12.5 cSt.

In the early days oils were monograde which meant they were in the same classification at both hot and cold e.g. 30W/30 which meant they were too thick then cold and okay when hot or vice versa (5W/5) and far too thin when hot.

Around 50 years ago additives were created that could reduce the loss in viscosity of the oils as they warmed up and hence they could be classed in multiple grades (multigrade) such as 5W30. These additives were called Viscosity Index Improvers:
 

Grayedout

Members
Messages
456
Reaction score
82
Location
Derbyshire
Car
2004 Accord 2.2
Viscosity Index Improvers (VII)

These are one of the most important additives in modern oils as they allowed the move from monograde to multigrade oils and give us all the various viscosity grades that we currently have. VII's are long molecules that curl up into tight balls when they are cold and so can easily move around each other and so do not have any effect on the viscosity of the fluid BUT as they warm up then the molecules open out into long chains which now not do not move freely across each other and so this increases the viscosity of the oil to a higher level than it should be at that temperature.

There are a large number of different types of VIII's that vary in both effectiveness and strength and for example a lower power VII is required to achieve say a 15W40 oil than something like a 10W60 where the required increase in natural viscosity is much greater.

All VII's do suffer from shearing where the long chains of molecules are broken up as the oil is stressed by some of the high pressure areas of the engine and so they start to lose their ability to maintain the viscosity of the oil at high temperatures and over time what started as a 5W30 for example may start to become a 5W25 or even a 5W20.

This is the first reason why you should change your oil at the recommended intervals!

More to come......
 

ampers

Members
Messages
34
Reaction score
2
Location
Bristol
Car
Accord 2.0 ex manual
So far so good, please carry on with your excellent post.
 

Alans27

Members
Messages
147
Reaction score
11
Location
Wirral
Car
Honda Accord 2.0 se
That quick word about synthetic is very true! Hence Castrol have been lableing some of their Magnatec oils as fully synthetics which is very misleading.
 

Grayedout

Members
Messages
456
Reaction score
82
Location
Derbyshire
Car
2004 Accord 2.2
Soot Handling

One of the key functions of the oil for diesel car owners is soot handing! I'm sure everyone has seen a diesel car accelerate quickly and suddenly create a huge cloud of black smoke, well this is soot and is caused by incomplete combustion. This is made worse by dirty injectors and also in the example above by overfuelling caused by using too much throttle!

But even in the normal diesel combustion process soot is generated and although most of this goes down the exhaust some of it finds it's way into the oil via blowby past the rings and also EGR re-circulation.

These individual soot particles are microscopic in size and will not cause any harm due to their size BUT what they love to do is to join up with other soot particles and begin to grow. If this is left to occur unchecked then the soot particles can grow to a size where they can cause abrasive wear on engine components as well as forming black deposits.

The way the oil handles this is with what are called dispersant additives which can be considered to be a little tadpole like structure where the head of the tadpole loves soot particles and the tail hates them so every time a soot particle enters the oil then a bunch of 'tadpoles' attach themselves to it with the heads on the soot and the tails facing away from the soot. This will then hold this tiny soot particle in suspension in the oil and will prevent it from attaching itself to any other soot particles and growing to a size that could cause problems.

Now in each oil there are only a fixed number of these dispersant 'tadpoles' and once they have attached themselves to a piece of soot then they are used up and cannot be used again so a fixed oil charge can only handle a fixed amount of soot so this is another reason to change your oil at regular intervals.

Why does the oil go black? Because the black colour comes from all the soot particles that are being held in suspension in the oil.

Now I have seen it reported that the 2.2 engine is very 'sooty' and produces a large amount of soot and so the 12,000 mile standard drain interval could be too long and maybe the dispersant additives are all used up in the first 10,000 miles and so during the last 2,000 miles of each drain the soot is free to grow and start to cause abrasive wear which may explain the timing chain wear issues that are seen in this engine.

My advice is use a good quality 0W-30 full synthetic oil and change it every 6,000 miles to make sure you don't run out of additives !
 

Stoobsy

BANNED
Messages
85
Reaction score
13
Location
Tewkesbury
Car
diesel '04 estate
Interesting, thanks

Grayedout said:
But even in the normal diesel combustion process soot is generated and although most of this goes down the exhaust some of it finds it's way into the oil via blowby past the rings and also EGR re-circulation.
I get how blow-by allows soot to get into the engine oil, but how does EGR make any difference to this?
 

Grayedout

Members
Messages
456
Reaction score
82
Location
Derbyshire
Car
2004 Accord 2.2
Stoobsy said:
Interesting, thanks


I get how blow-by allows soot to get into the engine oil, but how does EGR make any difference to this?
Because you are increasing the concentration of soot in the cylinder because there is now some soot coming back via EGR as well as the soot generated in the firing event so there is even more of it to get into the oil via blowby.

The EGR does not directly put soot into the oil but increases the possibility of it getting there by blowby.
 

mlkehunt

Members
Messages
89
Reaction score
25
Location
Norway
Car
08 I-CTDI sport
Sorry to necro this thread but I've got a question about ACEA specifications, because I can't find a clear cut answer on google.

Is 0w30 c2 fine to use in place of a5/b5? Rye oil ****ed up my order and sent me c2 in place of a5/b5
 

Grayedout

Members
Messages
456
Reaction score
82
Location
Derbyshire
Car
2004 Accord 2.2
Yes C2 would be okay for one change. It's a low SAPS oils designed to not pollute a DPF, that you won't need, but that way around won't do any harm.

Using an A5/B5 in a car that need a C2 would poison the DPF.
 

mlkehunt

Members
Messages
89
Reaction score
25
Location
Norway
Car
08 I-CTDI sport
right, thanks! why would it only be good for one change?

managed to find this thread https://typeaccord.co.uk/board/threads/oil-information.76/

it helped explain the acea certs and differences a little more. the parts below in particular
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 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.
 

Grayedout

Members
Messages
456
Reaction score
82
Location
Derbyshire
Car
2004 Accord 2.2
I just meant that if you may as well change back to A5/B5 as you don't need the C2 and it's probably more expensive.
 

mlkehunt

Members
Messages
89
Reaction score
25
Location
Norway
Car
08 I-CTDI sport
thanks again, I apologize for being so literal :p
I've got 20 liters to burn, £180 total with import tax and shipping, but if I were to source it locally I'd be paying £45 a liter for big brand stuff like mobil 1
 

Grayedout

Members
Messages
456
Reaction score
82
Location
Derbyshire
Car
2004 Accord 2.2
Top