Motor Oil Article Opinions wanted

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This article was recently posted on the Miata forum. No author given. I don't have time, at the moment, to really go over it, but anyone interested is welcome to comment on it. I'd like to say whether it is rubbish or not.

Full article;
http://www.wbengston.com/files/oil.txt

Excerpt;
quote:


Chapter One - Motor Oil 101

I think it is time to go over passenger car automotive engine oils in detail. I will be writing several articles to be published soon so I will try to get

some of it out here. I feel this is a very general topic for all car owners on this board.

This is a very difficult topic to comprehend. Everybody including good mechanics think they are experts in this field but few understand engine oils. Most of

what I hear is the opposite of the truth. It is however easy to see how people get mixed up as there is always some truth to the misconception.

Please forgive me if I am too wordy or even verbose at times. I will be redundant for certain. This will be in areas that people have to hear things over and

over again to get it right. Some will never be able to understand these concepts unfortunately. I base my thoughts on those whom I have been listening to in

various automotive chat rooms and discussion with mechanics. I will try to minimize technical terms and be somewhat vague rather than exact. I will round and

average numbers to make the point simple rather than mathematically exact. Thickness has the same meaning as viscosity. Viscosity is a measure of the

resistance of a fluid (liquid or gas) to flow. Fluids with high viscosity, such as molasses, flow more slowly than those with low viscosity, such as water.

Again, I am trying to explain general principals as I know them.

The greatest confusion is because of the way motor oils are labeled. It is an old system and is confusing to many people. I know the person is confused when

they say that a 0W-30 oil is too thin for their engine because the old manual says to use 10W-30. This is wrong.

More confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with motor oil.

It would be more correct to think that oil thickens when it cools to room temperature and THIS is the problem. In fact this is the problem. It is said that

90 percent of engine wear occurs at startup. If we are interested in engine longevity then we should concentrate our attention at reducing engine wear at

startup.

Oils are chosen by the manufacturer to give the right thickness at the normal operating temperature of the engine. I will say this average oil temperature is

212 F, the boiling point of water. On the track that temperature is up to 302F. It is important to realize that these are two different operating

environments and require different oils.

I will discuss driving around town first. Everything I say will be based on these conditions. At a later time I will discuss track conditions. Everything I

say will be as accurate as possible without looking everything up and footnoting. I am trying to be general not ultra specific.

One thing that is no longer important is the ambient temperature. Older automotive owner manuals often recommended one oil for the summer and another for the

winter. This is still necessary for air cooled engines but is no longer a consideration in pressurized water cooled engines. These engine blocks are kept at

around 212 F all year round. The oil is around the same temperature as well. This allows for a single weight oil all year round. Again, this is not the same

as on the track where the coolant temperature is slightly higher and the oil temperature is much higher.

Please forget those numbers on the oil can. They really should be letters as AW-M, BW-N or CW-P. The fact that we are dealing with a system of numbers on the

can makes people think that they represent the viscosity of the oil inside the can. The problem is that the viscosity of oil varies with its temperature. A

“30” weight oil has a viscosity of 3 at 302 F ( 150 C ) and thickens to 10 at 212 F ( 100 C ). It further thickens to a viscosity of 100 at 104 F ( 40 C )

and is too thick to measure at the freezing point of 32 F ( 0 C ).


30 weight oil:

Temperature ( F )....Thickness

302...........................3
212..........................10
104..........................100
32..........................250 (rough estimate)

The automotive designers usually call for their engines to run at 212 F oil and water temperature with an oil thickness of 10. This is the viscosity of the

oil, not the weight as labeled on the oil can. I want to stay away from those numbers as they are confusing. We are talking about oil thickness, not oil can

labeling. This will be discussed later. Forget the numbers on that oil can for now. We are only discussing the thickness of the oil that the engine requires

during normal operating conditions.

The engine is designed to run at 212 F at all external temperatures from Alaska to Florida. You can get in your car in Florida in September and drive zig-zag

to Alaska arriving in November. The best thing for your engine would be that it was never turned off, you simply kept driving day and night. The oil

thickness would be uniform, it would always be 10. In a perfect world the oil thickness would be 10 at all times and all temperatures.

If the thickness of oil was 10 when you got in your car in the morning and 10 while driving it would be perfect. You would not have to warm up your engine.

You could just get in the car and step on the gas. There would be little wear and tear on you engine, almost none. Unfortunately the world is not perfect.

The night before when you drove home from work the car was up the the correct operating temperature and the oil was the correct thickness, 10. Over night the

engine cooled to room temperature and the oil thickened. It is 75 F in the morning now (I do live in Florida). The oil thickness is now around 150. It is too

thick to lubricate an engine designed to run with an oil having a thickness of 10.

It is time to introduce the concept of lubrication. Most believe that pressure = lubrication. This is false. Flow = lubrication. If pressure was the thing

that somehow lubricated your engine then we would all be using 90 weight oil. Lubrication is used to separate moving parts, to keep them from touching. There

is a one to one relationship between flow and separation. If you double the flow you will double the separation pressure in a bearing. The pressure at the

bearing entrance is irrelevant.

In fact the relationship between pressure and flow is in opposition. If you change your oil to a thicker formula the pressure will go up. It goes up because

the resistance to flow is greater and in fact the flow must go down in order for the pressure to go up. They are inversely related. Conversely if you choose

a thinner oil then the pressure will go down. This can only occur if the flow has increased.

It seems then that we should all be using the thinnest oil money can buy. This is partly true. Let me use my 575 Ferrari Maranello as an example. I drive

this car around town. The manual of this car states the target pressure is 75 PSI at 6,000 RPM. The gold standard is that all engines should have a pressure

of 10 PSI for every 1,000 RPM of operation, not more, not less. After all, you do need some pressure to move that oil along, but only enough pressure, not

more. More pressure is not better, it can only result from the impedance of oil flow. Remember that oil flow is the only thing that does the lubricating.

Note that Ferrari is not saying what thickness of oil to use. That can only be determined by experimentation. My engine oil temperature is running around 185

F as I drive around town on a hot Florida summer day. I have found that the thinnest oil I can buy that is API / SAE certified is Mobil 1’s thinnest oil.

Even with this oil I get 80 PSI at 2,000 RPM. It is too thick for my application yet it is the thinnest oil money can buy. If I was on a hot Florida track in

mid-summer the oil temperature would probably get up to 302 F. I will guess that the pressure would only be 40 PSI at 6,000 RPM. The oil I am using would not

meet the requirement of 75 PSI at 6,000 RPM from Ferrari. I would have to choose a thicker oil for this racing situation. The oil I use now would be too thin

at that very high temperature. (This is only partly true. Higher RPM running engines use thinner and thinner oils to get more and more flow. I will discuss

this later).

High flow does more than lubricate. It is one of the things used to cool the hottest parts of your engine, the pistons, valve areas and bearings. This

cooling effect is as important as lubrication in your engine. If your engine is running hot use a thinner oil. The flow will increase and so will the

cooling. This is even more important in the racing condition.

Let us go back to the Ferrari manual. My older 550 Maranello only specified 5W-40 Shell Helix Ultra as the oil to use in all conditions. This car was

designed for racing. As it turns out Ferrari now recognizes that not every owner races their cars. The newer 575 manual now states to use 0W-40 for around

town situations even though Shell does not make this oil in the Helix Ultra formulation at this writing. They also recommend the 5W-40 by Shell if you insist

on the Shell product. It is also the recommended oil for most racing conditions.

Ferrari recommends Helix Ultra Racing 10W-60 “for hot climate conditions racing type driving on tracks”. Note that they now realize the difference between

the daily urban driver like me and the very different racing situation. These are widely different circumstances. I want to emphasize that they only want you

to use this oil while racing in “hot climate conditions”. If you are racing in Watkins Glen up north use the 5W-40. If you are racing in Sebring in the

middle of the Florida summer use the 10W-60. Around town in any climate, use the 0W-40.

It is time to dispel the notion that 0W-30 oil is too thin when our manual calls for 10W-30. A 0W-30 is always the better choice, always. The 0W-30 is not

thinner. It is the same thickness as the 10W-30 at operating temperatures. The difference is when you turn your engine off for the night. Both oils thicken

over the evening and night. They both had a thickness, a viscosity of 10 when you got home and turned your engine off. That was the perfect thickness for

engine operation.

As cooling occurs and you wake up ready to go back to work the next day the oils have gotten too thick for your engine to lubricate properly. It is 75 F

outside this morning. One oil thickened to a viscosity of say 90. The other thickened to a viscosity of 40. Both are too thick in the morning at startup. But

40 is better than 90. Your engine wants the oil to have a thickness of 10 to work properly. You are better off starting with the viscosity of 40 than the

honey - like oil with a viscosity of 90.

I repeat: More confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with

motor oil. It would be more correct to think that oil thickens when it cools to room temperature and THIS is the problem. In fact this is the problem.

This is the end of lesson number one.

 
There are some properties of synthetic oils that actually result is less wear than with mineral oils. These help increase your gas mileage as well. Due to a reduction of internal friction of the synthetic oil your engine will run a bit cooler. Wear increases as temperature increases, all other things being constant.

A main advantage that the synthetic has over the mineral based oil is the ability to lubricate at startup. Both types of oil have the same specifications at 104 F, 212 F and 302 F. It is the startup viscosity characteristics that separate these oils. Synthetic oils do not thicken as much on cooling. They have better fluidity as the temperature drops. This is telling me Synthetic is always better than mineral based oils.He goes on to say: This is worth repeating: The synthetic 10W-30 weight oil is based on a heavier 30 weight oil while the mineral based 10W-30 oil is based on a thinner 10 weight oil. They are both similar at operating temperatures yet the 30 weight based synthetic is actually less thick at startup and much less honey - like at low temperatures. This is the opposite of what common sense dictates.
So the old battle between one or the other remains unclear.With the depleation of additives being the turning point , even after all this time I still see a good UOA the only conclusive way to get a balance for our cars. I think this is the same guy who wrote how badly M1 sludged engines after running it past 10K miles. Don't quote me on that I am pretty sure I read that.The cost of changing is still low unless you drive a whole fleet of cars/trucks.I still like articles like the NYC cabs going twice the distance on conventinal oil with the same amount of wear. We can talk stats but wear is the bottom line.
 
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