Motor Oils It Is So Very Misunderstood. By Dr. Ali E. Haas. Lets Talk Motor Oil It is So Very Misunderstood Chapter One Motor Oil 1. 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. Solar Chargers For Aa Batteries Battery Rebuild Polaris Ebike Battery Bank Walmart Nimh Battery Recycling. 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. EHow Auto gets you on the fast track with repair, maintenance, and shopping advice. Whether youre jump starting a battery or insuring a new car, we can help. Power Clean 2000 Fuel System And Engine DeCarbonization Expert Manufacturer of Transmission Fluid Exchanger for Transmission Flush, Innovative Industrial. 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 0. W 3. 0 oil is too thin for their engine because the old manual says to use 1. W 3. 0. 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 9. 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 2. F, the boiling point of water. On the track that temperature is up to 3. F. 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 2. F all year round. The oil is around the same temperature as well. This allows for a single grade 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 3. 0 grade oil has a viscosity of 3 at 3. F 1. 50 C and thickens to 1. F 1. 00 C. It further thickens to a viscosity of 1. F 4. 0 C and is too thick to measure at the freezing point of 3. F 0 C. Oils are divided into grades not weights such as a 2. This represents the viscosity range at operating temperature. But it is NOT the actual viscosity as we shall see. The issue is that viscosity is temperature dependent. Lets look at a 3. Temperature F. Thickness. 30. 2. The automotive designers usually call for their engines to run at 2. F oil and water temperature with an oil thickness of 1. This is the viscosity of the oil, not the weight or grade 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 2. 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 1. In a perfect world the oil thickness would be 1. If the thickness of oil was 1. 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 to the correct operating temperature and the oil was the correct thickness, 1. Over night the engine cooled to room temperature and the oil thickened. It is 7. 5 F in the morning now I do live in Florida. The oil thickness is now around 1. It is too thick to lubricate an engine designed to run with an oil having a thickness of 1. 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 9. 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 old 5. Ferrari Maranello as an example. I drove this car around town. The manual of this car states the target pressure is 7. PSI at 6,0. 00 RPM. The gold standard is that all engines should have a pressure of 1. PSI for every 1,0. 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 was running around 1. F as I drove 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 1s thinnest oil. Even with this oil I get 8. PSI at 2,0. 00 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 3. F. I will guess that the pressure would only be 4. PSI at 6,0. 00 RPM. The oil I am using would not meet the requirement of 7. PSI at 6,0. 00 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 you may need to use a thinner oil. The flow will increase and so will the cooling. Ford Motorcraft Car Batteries Review.
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