ARTICLE: Synthetic oil vs Mineral oil

[Sam Kapasi]

Originally Posted by akshay1234

how much does a good flush cost?? and will they change the oil over there or do they only sell?

also does anybody know how many litres for a getz?

You can buy ABRO flush from there. I think it costs 200-300 bucks or so, I forgot. Check my spa thread.

It's an auto parts and stuff shop. Counter sales only. They don't do any work on your car.

[Rtech]

Ok. Lets clear things up here. Too many codes and number floating around.

First, an explanation of terms:
Viscosity Index (VI)
The rate of change of kinematic viscosity with temperature is the viscosity index. A high Viscosity Index indicates a smaller decrease in kinematic viscosity with increasing temperature.

The SAE had originally drawn up a scale to measure VI of oil, with 0 being the worst and 100 the best. However, with the improvement in technology, oils have gone over the 100 mark, hence the basic rule is that the higher the VI, the more stable the oil is over a wider range of temperatures. That is a good thing.

kinematic viscosity
Kinematic viscosity is a measure of the resistive flow of a fluid under the influence of gravity.

The higher the kinematic viscosity of an oil, the thicker the oil film that will ding to a metal surface. The higher the boiling point of crude oil, the greater its kinematic viscosity.

So what this means is that at a lower temperature you need that number to be lower, as that means the oil can flow to the area's required much sooner.

Now lets take 2 examples of 100% synthetic oils and compare their ratings as provided by the manufacturers themselves:

1. Motul 8100 X-cess 5W-40: For petrol & diesel engines, meeting API/CF standards

2. Mobil Delvac 1 5W-40: for Heavy duty diesel engines, meeting API/CI standards

Lets compare the specs (Motul / Mobil):
SAE Grade: 5W40 / 5W40
kinematic Viscosity @ 40ºC: 81.1 / 102
kinematic Viscosity @ 100ºC: 14 / 14.8
Pour point: - 39ºC / -45ºC
Flash point: 228ºC / 226 ºC
Viscosity Index: 173 / 151

As can be seen from the above example, Delvac 1 is a thicker oil which does not flow as well on starting up. Once upto temperature, they seem almost equal.

However, what is important is that the VI for Motul is far higher than that of Delvac, which means that Motul is a far more stable oil which will give you more predictable performance over a wider range of temperatures. Motul also has a marginally higher flash point.

None of these oils are bad, but for passenger car use, I would much prefer the Motul, as can be seen from the numbers.

Moral of the story: Don't do blindly by the ratings on the can.

[Akshay1234]

Originally Posted by Sam Kapasi

You can buy ABRO flush from there. I think it costs 200-300 bucks or so, I forgot. Check my spa thread.

It's an auto parts and stuff shop. Counter sales only. They don't do any work on your car.

ok.. thanks alot sam.cheers:

[adman77]

Originally Posted by ram

That quote is verbatim from:
Car Bibles : The Engine Oil Bible

Do read the entire document. It makes interesting reading.

Mixing Mineral and Synthetic oils - the old and busted concepts

For the longest time, I had this to say about mixing mineral and synthetic oils:

• If you've been driving around with mineral oil in your engine for years, don't switch to synthetic oil without preparation. Synthetic oils have been known to dislodge the baked-on deposits from mineral oils and leave them floating around your engine - not good. I learned this lesson the hard way! It's wise to use a flushing oil first.

• If you do decide to change, only go up the scale. If you've been running around on synthetic, don't change down to a mineral-based oil - your engine might not be able to cope with the degradation in lubrication. Consequently, if you've been using mineral oil, try a semi or a full synthetic oil. By degradation, I'm speaking of the wear tolerances that an engine develops based on the oil that it's using. Thicker mineral oils mean thicker layers of oil coating the moving parts (by microns though). Switching to a thinner synthetic oil can cause piston rings to leak and in some very rare cases, piston slap or crank vibration.

• Gaskets and seals! With the makeup of synthetic oils being different from mineral oils, mineral-oil-soaked gaskets and seals have been known to leak when exposed to synthetic oils. Perhaps not that common an occurrence, but worth bearing in mind nevertheless.

Mr. Ram. There are a lot of links on the net which tell you about the numerous advantages of synthetic oil also. IMHO, it doesn't make sense to search for links that degrade synthetic oils just to try and force your point of view. A good opinion is the one which is given without a bias and is free and fair.

[Akshay1234]

adman77 - i dont see whats wrong in him giving some precautions.

[Sam Kapasi]

Originally Posted by adman77

Mr. Ram. There are a lot of links on the net which tell you about the numerous advantages of synthetic oil also. IMHO, it doesn't make sense to search for links that degrade synthetic oils just to try and force your point of view. A good opinion is the one which is given without a bias and is free and fair.

adman,

Ram simply gave some very correct precautions. None of them degrade synthetic oil. They simply make the user cautious about the change to synthetic. His personal point of view may or may not subcribe to the usage of synthetic oils and he is entitled to his opinion. He simply quoted an article that provided some information.

Moreover he gave his opinions last year (your quoted post is from october 06) and the matter was discussed in detail.

Reading the entire discussion will be a source of great knowledge for you.

Cheers

[tsk1979]

Originally Posted by Rtech

Moral of the story: Don't do blindly by the ratings on the can.

Ok, correct
One question though.
So you are ready to Put API-CF oil in a car which has it clearly mentioned API-CH minimum required?
Also when you talk about lower temperatures, the numbers mentioned on the low side come into play at -10 or so, if your ambient temp never falls below 15 degrees the lower number is somewhat meaningless.

[adman77]

Hey guys, going for a flush and an oil change for my Corsa 1.4 tomorrow. Getting Mobil1 0w-40 with K&N oil filter. Will let you know how it feels after the change.

[nitrous]

Don't get 0W40,adman.Its for very cold weather.
Stick to 5W50.

[Rtech]

Originally Posted by tsk1979

Ok, correct
One question though.
So you are ready to Put API-CF oil in a car which has it clearly mentioned API-CH minimum required?

Again, so just seem to be getting me wrong! Yes, you need the standards listed in your service manual. All I'm saying is that dive a bit deeper and check out the data sheet to get a more accurate picture.

Originally Posted by tsk1979

Also when you talk about lower temperatures, the numbers mentioned on the low side come into play at -10 or so, if your ambient temp never falls below 15 degrees the lower number is somewhat meaningless.

You have not read what I posted correctly.
kinematic Viscosity @ 40ºC: 81.1 / 102

KV is measured at 40ºC on the low side. Something an engine will get upto within a few seconds of starting. This is the most critical time when an oil comes into play. Not sure where you got the -15ºC from?

[tsk1979]

Originally Posted by Rtech

Again, so just seem to be getting me wrong! Yes, you need the standards listed in your service manual. All I'm saying is that dive a bit deeper and check out the data sheet to get a more accurate picture.



You have not read what I posted correctly.
kinematic Viscosity @ 40ºC: 81.1 / 102

KV is measured at 40ºC on the low side. Something an engine will get upto within a few seconds of starting. This is the most critical time when an oil comes into play. Not sure where you got the -15ºC from?

Yup, I agree deep diving is necessary. But there are some things which will not be very apparent. For example a higher API grade oil will offer better lubrication and has different set of additives etc., So just viscosity is not really important here.
Also I may be wrong here, but isn't an oil which is more viscous at 40 degrees C a better bet.
Of course in case of a thicker oil you will need to warm up the engine for a minute before revving to prevent startup damage.
I prefer diesel specific oil because its a known fact that if you make an oil which meets API-SM or API-SL standards for petrol engines you will not be able to meet API-CH etc., for diesel.
Similarly, all oils I have seen having API-CHor higher ratings cannot be used for Petrol engines.
This is the thing which gravitates me towards API ratings as major criteria. I am not saying Viscosity etc., are not important. All I am saying is that I tend to believe that an API-CI oil will do better in your engine than a API-CF oil. Here I am not talking about brands specifying different standards such as VW etc.,
When I chose have to choose an oil, the first criteria for me would be API rating, the second would be the detergent content, and other things will come later.
I do not rate viscosity very high on scale because many additives in market like STP etc., claim to make the oil "thicker" at higher temperatures.
So I sort of came to the understanding that at running temperatures(80 degrees odd) an oil which is thicker will be better for engine.
0W30 oil in Delhi heat will be like water and have as much protection as water. We use 20W50 or 15W50 or 5W50 so that oil is thicker at that high temperature.

[Rtech]

Ok. Seem's like you have your mind made up on a certain aspect so I'm not about to try and change that. All I'm doing is listing out facts, what somebody chooses to do with them is an individual choice. As I also mentioned, neither is bad, and all these are far superior to mineral oil.

Also I may be wrong here, but isn't an oil which is more viscous at 40 degrees C a better bet.

More viscous means it takes longer to flow through the engine. One of the main reasons why synthetics are superior is their ability to survive cold temperatures without much change in its state. When you first start your engine, the priority of the oil is to lube 100% of your engine in the quickest possible time. This can be done more efficiently if the oil flow faster, which it will do if it is less viscous.

Once the engine is upto temperature, the oil has to cool as well as lubricate. The ability of an oil to do these functions to its fullest depends on its ability to maintain its chemical state within certain tolerances for as long as possible in varied temperatures. There is a an industry standard by which this is measured, and that is called Viscosity Index.

So I sort of came to the understanding that at running temperatures(80 degrees odd) an oil which is thicker will be better for engine.
0W30 oil in Delhi heat will be like water and have as much protection as water.

Yes, that is correct. But we are not talking about the grading of the oil are we?

In the two examples given above, the VI of the CF oil is higher than the VI of the CI oil. That means that the CF oil in this case will provide a more constant working environment than the CI oil (in this example).

As mentioned above, the VI is the tell all of the oil. It shows how much an oil will thin with an increase in temperature. Its as simple as a higher VI means the oil will be more resistant to thinning.

When I chose have to choose an oil, the first criteria for me would be API rating, the second would be the detergent content, and other things will come later.

How will the detergent help your engine when cold if the oil hasn't reached all area's of your engine? The sooner it does, the sooner your engine is protected. API ratings etc are the base. You can get a 0W30 oil and 15W50 oil that both meet the same API standards.

What synthetics do is allow the oil to function at its best over a wider range of temperatures. It's as simple as that. It is not necessary that an oil that is thicker when in the can will remain thicker when it is in an engine running at 100 degrees C. The example above proves that. In this example the motul is thinner and quicker flowing on cold, but at 100 degrees C, both the motul and Delvac are almost the same thickness. But, the VI of the Motul is higher meaning it will thin less with increasing temperatures, and herein lies the advantage.

[Sam Kapasi]

I would like to interject here and say that I am greatly enjoying this quality debate and am learning some fantastic things about oil. Well dome tsk and Rtech. As you might have figured out, oil is for some inane reason, a topic of interest to me and I'm really learning here.

Man, you know your stuff. You guys should be moderators on this forum!!

Thanks for this excellent technical discussion.

[BUSA]

Man, you know your stuff. You guys should be moderators on this forum!!

Sam aren't they moderators?

@ Rtech - Could you please tell how good is Motul and what is the cost per liter? And are you running a Conical Airfilter in your car?

[Rtech]

Motul costs the same as Mobil. Realistically speaking, there is nothing between these top-line oils. Just comes down to your individual preference and more importantly, availability. Motul is almost impossible to find here. They have no official dealers! City Motors keeps Motul, but only in the 0W30 grade. I've been after them to get the 5W40, but doesn't look like that's happening.

No, I am running an OE replacement Pipercorss foam filter.