ARTICLE: Synthetic oil vs Mineral oil

[Jeroen]

Originally Posted by bullrun87

I agree with most of what you have said, more coolant will bring up the boiling point of the coolant water mix. But the pressure has a profound effect on the boiling point of all known liquids. For example water boils at 100 deg C at atmospheric pressure but at a pressure of 1 bar above atmospheric it will boil at 120 deg C!!
So lets say if your running your car with water and temp in the coolant circuit is 105 deg C but all of the water in the circuit will still be liquid due to the higher pressure. but if you open the coolant nozzle at the top, steam will come out because the pressure is now atmospheric and water needs to be steam at 105deg C and atmospheric pressure. Similarly a coolant water mixture will also boil at higher temperatures if pressures are higher than atmospheric.

I responded to your earlier post in which you said and I quote:

I agree sir, coolant is denser than water so higher percentage of coolant will result in higher coolant system pressure but correspondingly the heat transfer ability of the system diminishes.

That is not the case. A higher percentage of coolant does not result in a higher coolant system pressure, irrespective of density. The percentage of coolant doesn't determine the coolant system pressure as such. The coolant system pressure is a result of a number of design criteria: the volume of the total cooling system, the liquid and gas volumes inside the system, the normal operation temperature and the physical properties of the actual liquid (coolant/water mix) you put in it. (plus a few more).

Modern car engine cooling system are typically closed system. As per my earlier post, as the engine and the cooling system heats up, the volume of the coolant expands. As the system is a closed one, the pressure builds. At this higher pressure the coolant, or any liquid for that matter, boils at a higher temperature. Adding coolant to water ensures an even somewhat higher boiling temperature. Effectively requiring a little less pressure!

But the coolant is there for more important reasons as well, e.g. protection of your cooling system against corrosion, ensuring it doesn't freeze below zero degree C and it also help lubricate the water pump.

But the density of the coolant mix or percentage doesn't determine the actual coolant pressure. Physics simply don't work that way.

Jeroen

[bullrun87]

Originally Posted by Jeroen

I responded to your earlier post in which you said and I quote:
That is not the case. A higher percentage of coolant does not result in a higher coolant system pressure, irrespective of density. The percentage of coolant doesn't determine the coolant system pressure as such. The coolant system pressure is a result of a number of design criteria: the volume of the total cooling system, the liquid and gas volumes inside the system, the normal operation temperature and the physical properties of the actual liquid (coolant/water mix) you put in it. (plus a few more).

I agree with most of the things you have stated, the coolant system pressure will depend mainly on

1) Coolant system design, especially the size of hozes and pipes
2) Physical properties of fluids including density(will elaborate more on that)
3) Operating temperature
I am stating that the system pressure will depend on density partly due to my experience with designing and operating industrial pumping curcuits. There is a continuous flow of coolant+water in the circuit. This is achieved by the water pump. This pump is a centrifugal pump and the pressure developed by this pump in a closed loop circuit is dependent on the resistance in the circuit(narrower hoses=more resistence=higher pressures) and density of the fluid being pumped. Simply put a pump requires to put out more pressure for a denser fluid(coolant is denser than water). Hence I state that increasing the coolant/water ratio will do the following things
1) Increase system pressure due to higher density
2) Ensure it doesn't freeze below zero degree C
3) Increase the boiling point
4) Presence of coolant aids in pump lubrication and prohibits corrosion
5) lower the heat carrying capacity of the system as coolant is not as good a heat transfer agent as water

We have changed an engine oil discussion into something completely
different. Mods will not be pleased

[Jeroen]

Originally Posted by bullrun87

I am stating that the system pressure will depend on density partly due to my experience with designing and operating industrial pumping curcuits. There is a continuous flow of coolant+water in the circuit. This is achieved by the water pump. This pump is a centrifugal pump and the pressure developed by this pump in a closed loop circuit is dependent on the resistance in the circuit(narrower hoses=more resistence=higher pressures) and density of the fluid being pumped. Simply put a pump requires to put out more pressure for a denser fluid(coolant is denser than water).

Well, its been a while since I looked into pumps. But here is what I know:

Density has no effect on either the volumetric flow rate or the head developed by a centrifugal pump. This essentially means that for a given volume flow rate a change in density will change the mass flow rate. Thus if the density increases the mass flow rate will increase and if the density decreases the mass flow rate will decrease.

The most immediate noticeable effect of density change if you are not measuring the mass flow will be in the absorbed power of the pump driver. This is evident from the absorbed power equation for any pump.

P = Q*H*ρ*g / 3600*η

where:

P = absorbed power, kW
Q = volumetric flow rate, m3/h
H = Differential head, m
ρ = density of liquid, kg/m3
g = gravitational constant , 9.81 m/s2
η = efficiency, dimensionless

So please share how density affect pressure. I'm aware that a lot of people talk about designing pumps, but what they are doing is sizing a pump for a particular application. That is not designing. There are simple tables and graphs for that, usually based on water and often showing specific gravity. Those tables might give the impression of the pressure raising. But what effectively happens is you need to put more power on the pump to maintain the same flow.

The power for your typical water coolant pump in a car engine is not a factor. The pump is driven directly from the engine. So whatever RPM and whatever density that's the power that the engine will put into the pump so to speak.

Do you really design pump? What firm, what kind of pumps and applications If you do I might have a few more questions for you. Just show me some evidence to the contrary to what I just said.

In reality we are talking about a minimal change of density too. At a 50/50 mix of coolant (glycol) and water the density increase is approx 8%.

Jeroen

[bullrun87]

Originally Posted by Jeroen

Well, its been a while since I looked into pumps. But here is what I know:

Density has no effect on either the volumetric flow rate or the head developed by a centrifugal pump. This essentially means that for a given volume flow rate a change in density will change the mass flow rate. Thus if the density increases the mass flow rate will increase and if the density decreases the mass flow rate will decrease.

The most immediate noticeable effect of density change if you are not measuring the mass flow will be in the absorbed power of the pump driver. This is evident from the absorbed power equation for any pump.

P = Q*H*ρ*g / 3600*η


So please share how density affect pressure. I'm aware that a lot of people talk about designing pumps, but what they are doing is sizing a pump for a particular application. That is not designing. There are simple tables and graphs for that, usually based on water and often showing specific gravity. Those tables might give the impression of the pressure raising. But what effectively happens is you need to put more power on the pump to maintain the same flow.


Jeroen

I don't design pumps. I designed pumping systems for the oil and gas and petrochemical industry until last year. Any centrifugal pump develops the same head irrespective of the fluid it is pumping(as long as the fluid is not very viscous). It operates on a curve, so for a given head it will operate at a fixed volumetric flow rate. So you're right density has no effect on volumetric flow rate or the head developed by the pump. But density does affect the power required by the pump as can be seen by the formula you have posted. Density change also affects the pressure at the discharge of the pump. Let's assume a simple pump with suction pressure of 1 bar gauge. Now consider pumping water with this ficticious pump that develops 100 m head. Now lets calculate the discharge pressure. 100 m head corresponds to a pressure increase(difference betweeen suction and discharge pressure) of 10 bar approximately.
P=head *density*gravity.
So the discharge pressure of the pump will be 1+10=11 bar gauge. Now if I replace this water with a fluid of density 20 percent more than water and as long as the fluid is not very viscous, the pump will still produce 100 m head at same volumetric flow rate. but the pressure increase due to pump in this case will increase by a factor of 1.2 to 12 bar approximately using p=head*density*gravity since density has increased by 20 percent. So discharge pressure will be 1+12=13 bar gauge
So a density increase has changed the discharge pressure of the pump. Power consumed will also be higher as per your formula. Similarly if u use a lighter fluid say petrol or kerosene with density lesser than water with this fictitious pump discharge pressure will be lower and power consumption will also be lower.

[vnabhi]

Originally Posted by vnabhi

May I know why you are suggesting 5w50 when the manual for Fiesta 1.6 prescribes 5w30? I'd posted the same query on my LTO thread, and the respondents were suggesting 5w40, and that 5w50 would be an overkill.

Incidentally, the trusted S.A. at Mody Ford was also suggesting 5W50.

This apart, the Mobil1 website for India lists only 5W50 and 0w40 types, I don't see any other types.

http://www.mobil1.co.in/products/

Meantime, prices seem to have increased. The quotation I got from a Mobil dealer is Rs 1375 per liter for 5W30 (surprisingly available though not listed in mobil's website) and Rs 1350 for 5w50.

I need inputs fast, as I plan to give my car early next week for service.

Thanks in advance.

Originally Posted by csateesh

Hi vnabhi - Yes I do know that the recommended grade for Fiesta 1.6 is 5w30. I had recommended 5w50 as I haven't seen 5w30 in Bangalore atleast.

Since the ambient temperatures in India are high except a few places going with 5w50 which is slightly thicker at cold temperatures should be a safe option.

But if you are able to find the exact 5w30 pls. go ahead and use the same

My quest for Mobil1 5W50 was getting murkier by the day. Most dealers in Hyderabad did not have it in stock, but some said they could get it for me from another outlet, at a rate of 1350 per liter.

When I rang up my S.A. in Ford A.S.S, they said they had it in stock and would cost Rs 1200 per liter, which seemed to be a lot cheaper, as my car needed 4.1 liters.

I gave one final try and called Xenex. They said they'd deliver it at home for a price of Rs 1000 a liter, but I'd have to buy 4.5 liters as it comes in 3.5 liter and 1 liter packs. Though I needed less than that, I thought it would be a good idea to keep some for future top ups. Xenex also said that according to the Mobil1 rep in Hyd, the same oil is sold as 5W50 for Porsche and as 5W40 for Skoda.

I find this quite intriguing, moreso when their website only mentions 5W50 and OW40.

Users of Mobil1 may please update this thread on what they paid per liter.

[akshay4587]

Originally Posted by vnabhi

My quest for Mobil1 5W50 was getting murkier by the day. Most dealers in Hyderabad did not have it in stock, but some said they could get it for me from another outlet, at a rate of 1350 per liter.

When I rang up my S.A. in Ford A.S.S, they said they had it in stock and would cost Rs 1200 per liter, which seemed to be a lot cheaper, as my car needed 4.1 liters.

I gave one final try and called Xenex. They said they'd deliver it at home for a price of Rs 1000 a liter, but I'd have to buy 4.5 liters as it comes in 3.5 liter and 1 liter packs. Though I needed less than that, I thought it would be a good idea to keep some for future top ups. Xenex also said that according to the Mobil1 rep in Hyd, the same oil is sold as 5W50 for Porsche and as 5W40 for Skoda.

I find this quite intriguing, moreso when their website only mentions 5W50 and OW40.

Users of Mobil1 may please update this thread on what they paid per liter.

Pretty Sure that Xenex is trying to pass on some other oil as Mobil 1 5W50 since it never came in a 3.5L pack.Its either 4L or 1L.
I tried looking around 5W50; but was not able to find it.
Finally settled for 0W40 at 950/L.
I would recommend that you go in for 0W40.

[vnabhi]

Originally Posted by akshay4587

Pretty Sure that Xenex is trying to pass on some other oil as Mobil 1 5W50 since it never came in a 3.5L pack.Its either 4L or 1L.
I tried looking around 5W50; but was not able to find it.
Finally settled for 0W40 at 950/L.
I would recommend that you go in for 0W40.

Thanks. I will verify the oil Xenex has before buying it. I guess the container will be sealed and have the oil type mentioned on it, right?

[akshay4587]

Originally Posted by vnabhi

Thanks. I will verify the oil Xenex has before buying it. I guess the container will be sealed and have the oil type mentioned on it, right?

There a quite a few varieties of Mobil Fully Synthetic oils in the Market.
Mobil 1 and Delvac 1 are the best in their respective segments.

[Jeroen]

Originally Posted by akshay4587

Mobil 1 and Delvac 1 are the best in their respective segments.

Why? How do you verify / test that?

Jeroen

[akshay4587]

Originally Posted by Jeroen

Why? How do you verify / test that?

Jeroen

The best among the range of Mobil oils being sold in India.
I can only vouch for Mobil 1 and Delvac 1 based on their performance collectively coming upto 2L kms.

PS:I never went for any lab tests.

[Jeroen]

Originally Posted by bullrun87

P=head *density*gravity.
So the discharge pressure of the pump will be 1+10=11 bar gauge. Now if I replace this water with a fluid of density 20 percent more than water and as long as the fluid is not very viscous, the pump will still produce 100 m head at same volumetric flow rate. but the pressure increase due to pump in this case will increase by a factor of 1.2 to 12 bar approximately using p=head*density*gravity since density has increased by 20 percent. So discharge pressure will be 1+12=13 bar gauge
So a density increase has changed the discharge pressure of the pump. Power consumed will also be higher as per your formula. Similarly if u use a lighter fluid say petrol or kerosene with density lesser than water with this fictitious pump discharge pressure will be lower and power consumption will also be lower.

Agree, to be more precise:

The head of a pump in metric units can be expressed in metric units as:

h = (p2 - p1)/(ρ g) + v2(2)/(2 g)

where

h = total head developed (m)
p2 = pressure at outlet (N/m2)
p1 = pressure at inlet (N/m2)
ρ = density (kg/m3)
g = acceleration of gravity (9.81) m/s2
v2 = velocity at the outlet (m/s)


Also, the pressure in an engine's cooling water circuit is rarely higher then 1 bar. So from a practical point of view, for car engines at least, this effect is negligible I would say.

[Jeroen]

Originally Posted by akshay4587

The best among the range of Mobil oils being sold in India.
I can only vouch for Mobil 1 and Delvac 1 based on their performance collectively coming upto 2L kms.

PS:I never went for any lab tests.

So, again, why is it the best? On what criteria?
So what is the performance then? How did you measure the performance during the 2L kms?

Jeroen

[akshay4587]

Originally Posted by Jeroen

So, again, why is it the best? On what criteria?
So what is the performance then? How did you measure the performance during the 2L kms?

Jeroen

Best amongst all other Mobil oils on sale here; Came to a conclusion by comparing their ratings;and overall reviews over internet.
When i said performance over 2L kms; i didn't go around measuring clearances and other parameters.
I was just quoting the usual NVH levels and engine behavior.

[bullrun87]

Originally Posted by Jeroen

Agree, to be more precise:

The head of a pump in metric units can be expressed in metric units as:

h = (p2 - p1)/(ρ g) + v2(2)/(2 g)


Also, the pressure in an engine's cooling water circuit is rarely higher then 1 bar. So from a practical point of view, for car engines at least, this effect is negligible I would say.

The pressure increase when using no coolant and say 50 percent coolant would be about 5 to 10 percent. I just wanted to point out that sometimes when using a single pump for several different fluids the effect on horsepower and discharge pressure can be too significant in some cases to neglect so I have developed a habit of always considering density changes in all systems I analyse.

[Jeroen]

Originally Posted by akshay4587

Best amongst all other Mobil oils on sale here; Came to a conclusion by comparing their ratings;and overall reviews over internet.
When i said performance over 2L kms; i didn't go around measuring clearances and other parameters.
I was just quoting the usual NVH levels and engine behavior.

So basically your car ran fine over 200.000 kilometers and you had no problems relating to (apparent) oil.

Truth be told, any car engine, properly looked after, properly maintained in accordance with the manufacturers specifications and using oil in accordance with the recommended specification will all run 2L ams without issues relating to oil.

Given that I assume everybody puts the correct spec oil in their engines, and don't take notice of people on the internet who advise differently, the most prominent factors in engine wear, much more prominent then the oil, are:

- Correct oil filtrations (i.e. the correct filter and changed at the correct intervals)
- Correct air filtration (i.e. the correct filter and changed at the correct intervals)
- Ensuring the cooling system works correctly, especially avoiding too low temperatures due to faulty thermostats etc.
- Engine use, (e.g. city versus highway etc)

As long as you use the correct specification of oil, the brand doesn't matter much. At least not in practical terms. Other factors, as mentioned above are far more important. Surprisingly, on car forums everybody seems to want to debate endlessly what is really not a big factor.

But I'm not complaining. I never buy new cars, so the more money gets spend on the cars by their first/second/third owner before I would buy it the more beneficial it is to me. This is another consideration I don't hear much about. If you replace your car every say 5 years or at 100 or 150.000 kilometers, how relevant is the oil quality then? Again, the answer is, as long as the oil complies with the manufacturers recommendation it is very likely not very relevant for the owners during that first 100-150K. It becomes relevant for the next 100-150K.

Jeroen