www.geocities.com/Yosemite/Gorge/6770/motor_oils.htm
O I L
SYNTHETIC vs REGULAR, ADDITIVES, GRADES
INTRODUCTION
SYNTHETIC OIL
MULTI-VISCOSITY: WHICH GRADE TO USE
Introduction
Look carefully on 5W-50, 5W-40 by Castrol and Shell "Synthetics" which are actually hydro processed oils and both use mineral oil-based stock from Shell. In most cases high polymer content you can see right away by the percentage of ash. That's what will be left in you engine (cylinders, valves oil channels) after oil circulates there; also, some burns in combustion chamber. It sure forms more sludge and deposits in the engine. This has caused problems in diesel engines, but fewer polymers are better for all engines. The wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to the high polymer content. It is the oil that lubricates, not the additives. Oils that can do their job with the fewest additives are the best.
Very few manufactures recommend 10W-40 anymore, and some threaten to void warranties if it is used. And even though 20W-50 has the same 30 point spread, it requires fewer polymers because it starts with a heavier base. AMSOIL (a synthetic) can formulate their 10W-30 and 15W-40 with no viscosity index improvers but uses some in the 10W-40 and 5W-30. Mobil 1 uses no viscosity improvers in their 5W-30, and, presumably, for the new 10W-30.
Viscosity Index is an empirical number indicating the rate of change in viscosity of an oil within a given temperature range. Higher numbers indicate a low change, lower numbers indicate a relatively large change. The higher the number the better. This is one major property of an oil that keeps your bearings happy. These numbers can only be compared within a viscosity range. It is not an indication of how well the oil resists thermal breakdown.
Flash point is the temperature at which an oil gives off vapors that can be ignited with a flame held over the oil. The lower the flash point the greater tendency for the oil to suffer vaporization loss at high temperatures and to burn off on hot cylinder walls and pistons. The flash point can be an indicator of the quality of the base stock used. The higher the flash point the better. 400 F is the minimum to prevent possible high consumption. Flash point is in degrees F.
Pour point is 5 degrees F above the point at which a chilled oil shows no movement at the surface for 5 seconds when inclined. This measurement is especially important for oils used in the winter. A borderline pumping temperature is given by some manufacturers. This is the temperature at which the oil will pump and maintain adequate oil pressure. This was not given by a lot of the manufacturers, but seems to be about 20 degrees F above the pour point. The lower the pour point the better. Pour point is in degrees F.
Percent sulfated ash is how much solid material is left when the oil burns. A high ash content will tend to form more sludge and deposits in the engine. Low ash content also seems to promote long valve life. Look for oils with a low ash content.
Percent zinc is the amount of zinc used as an extreme pressure, anti- wear additive. The zinc is only used when there is actual metal to metal contact in the engine. Hopefully the oil will do its job and this will rarely occur, but if it does, the zinc compounds react with the metal to prevent scuffing and wear. A level of .11% is enough to protect an automobile engine for the extended oil drain interval, under normal use. Those of you with high revving, air cooled motorcycles or turbo charged cars or bikes might want to look at the oils with the higher zinc content. More doesn't give you better protection, it gives you longer protection if the rate of metal to metal contact is abnormally high. High zinc content can lead to deposit formation and plug fouling.
So why isn't synthetic oil in every engine, transmission, and differential? Because it costs more to produce. The key ingredients are decene molecules. Decene is a linear molecule with 10 carbons, and it's synthesized by first linking together five molecules of ethylene, each of which contains two carbons. The second synthesis step involves polymerization of the decene. Two or more decene molecules are combined to form short chain-length polymers, and from these, PAOs result. No doubt, it's a capital-intensive manufacturing process that unavoidably leads to higher retail prices than cheaper-to-produce mineral oil.
From: http://www.hotrod.com/techarticles/79838/
In Europe, blenders still need to use some PAO in order to meet the toughest ACEA specs. In the US, Mobil 1, Amsoil, Red Line and Royal Purple are the only ones you can be (reasonably) SURE OF still using PAO. If you can get a material safety data sheet (MSDS) for the oil you are interested in, look for PAO or polymer or oligomer of 1-decene as a component for a tip-off. Synthetic blends contain some amount (not defined, as far as I know) of synthetic basestock. The small amount of viscosity modifier present in most multi-grade oils probably fulfils this requirement, making synthetic blends another profit centre for the oil blenders.
- From: http://faq.f650.com/FAQs/OILFAQ.htm
5W-30 Lowest Operating Temperature: -13 F Provides excellent fuel economy and low temperature performance in most late model automobiles. Especially recommended for new cars.
10W-30 Lowest Operating Temperature: 0° F Most frequently recommended viscosity grade for most automobile engines, including high performance multi-valve engines and turbo-charged engines.
10W-40 Lowest Operating Temperature: 0° F The first multi-grade introduced. A good choice for controlling engine wear and preventing oil breakdown from oxidation due to hotter-than-normal running conditions. Note: Always check your owner's manual or warranty requirements before using this grade.
20W-50 Lowest Operating Temperature: 15° F Provides maximum protection for high performance, high RPM racing engines. Excellent choice for high temperature and heavy loads such as driving in the desert or towing a trailer at high speeds for long periods of time.
SAE 30 Lowest Operating Temperature: 15° F For cars and light trucks, where recommended by manufacturers.
SAE 40 Lowest Operating Temperature: 32° F Not recommended when cold temperature starting is required.
• Thinner oil (e.g., 10W30) lubricates narrow passages better in cold conditions; less prone to "sludge"; better for newer, "tighter" engines;
• thicker oil (e.g., 10W40, 20W50) reduces oil consumption (burning) in older, worn engines; better protection in hot conditions;
What does "multi-viscosity" mean? (I would think it would be next-to-impossible to create anything else).
"Multi-viscosity" doesn't refer to any changes in the oil's thickness caused by changes in temperature. It is a simply a rating of the _relative_ viscosity of an oil compared to other oils -- which could be thinner or thicker.
From http://home.att.net/~ferrari/oil1.htm
{Oil Pressure Gauge Jittery]
[http://www.ford-trucks.com/dcforum/DCForumID77/884.html]
If pressure still flutters you have either an oil leak (internal - like a bad journal), an oil passage blockage (try changing the oil AND FILTER), a stuck pressure releif valve (relpace this for a few bucks), or a problem with the pump (ouch).
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[Idea: Maybe some debris got loose & clogged the filter, thus interfering with the flow... othe rmessages mention High Filtration oil filters possibly causing this,,, maybe excess debris is crating the same effect - RJ]
[http://autos.groups.yahoo.com/group/fordexplorer/message/359]
I was thinking that without this possibly it is what is affecting the gauges. The gauge has a resistor on the back( for lack of a better word ) which keeps the gauge in a sort of comfort zone for the driver. Put an aftermarket gauge on the and bypass it around the factory on and you will be amazed at how fast the oil pressure rises and falls compared to what the factory on is doing. What I was thinking (but without proof) is if the oil filter does not have the valve or it is malfunctioning the resistor (again lack of a better word) might read it as a failure giving you a low oil pressure readout. Mainly because it has fallen outside its set operating values. I have no proof this is what happening and it is just a theory based on what I had read.