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kakarot -> RE: which is the best oil (9/11/2005 10:14:26 AM)
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wrong. 10w-30 means
it will flow like 10 in 0 C and 30 in 100C it has nothing to do with lubrication not direct any way.
there is a addictive that they add to make so it doesn't lubricate called VII, well why wont you just read it
quote:
An oil sold as 10w-40 is no thicker than 10 weight oil under Winter (10w) conditions, meaning below freezing. The 40 means it is no thinner than 40 weight oil at 212° Fahrenheit. So, the first number tells us the performance of the oil at or below the temperature of freezing water, and the second number tells us the performance at the temperature of boiling water. The chemicals added to the oil to accomplish this are called Viscosity Index Improvers (VIIs).
To make a 10w-40 oil, the manufacturer would start out with a 10 weight oil as the base stock. All by itself, this oil would thin out so much at normal operating temperatures that the oil film would be useless. So, they add these very special very long molecules, the VIIs. The VII molecules are as much as 1000 times as long as an oil molecule. The VII molecules curl up in a little ball at room temperature, but as the temperature gets higher they uncurl and stretch out, like a cat sleeping in the sunlight. The more stretched out the molecule is, the more it impedes the normal flow of the oil, thus raising the effective viscosity. Now, this sounds just a little too good to be true. Well, there are two catches: first, these molecules are not lubricants, so the more of them that you add the less oil you have sitting around lubricating things. Secondly, these VII molecules can be broken into pieces by various pressures and forces, like being squeezed through the transmission gears in a motorcycle or the hydraulic valves in a diesel engine. Every time a VII molecule gets broken, the oil loses some of its high temperature viscosity. Synthetic oils made from pure PAOs and/or Diesters typically have very few VIIs, so these oils are far less subject to viscosity breakdown due to shearing of the VII package. As a result, synthetics are far more stable in a motorcycle engine.
10w-30 oil increases its viscosity at high temperatures by a factor of three, which requires a significant amount of these VII molecules. 10w-40 oil increases its high temperature viscosity by a factor of four, which requires even more even longer molecules. 20w-50, which sounds a lot like 10w-40, only increases its high temperature viscosity by a factor of two and a half, so it requires fewer of these molecules than even 10w-30. 15w-40 also increases its high temperature viscosity by about two and a half, so this oil is also substantially more stable than 10w-40. Most passenger car oils today use inexpensive VII molecules that break apart relatively easily. Conversely, most diesel engine oil VIIs are chosen from more expensive chemicals that are more shear stable, since an oil change in a large diesel is expected to last for 15,000 to 150,000 miles.
I usually use S/C oil that works both on diesel and gassoline engine, the reason is that diesel oil is better cleaner and have a bit better proparties. if you have a lot of burned oil in your engine then use S/C class oil to clean it up. I have mazda626 and idiots in my garage put in regular oil, it went bad in 1000 miles, so I had to switch into syn-blend each about 2.5k-3.5k for couple times then switched in for Mobil1 extended performance and now I have about 5K on it and still running.
for my audi I will use syn blend this time 5w-20 or 10w-30 for winter.
The reson why you should NOT blend organic and syn oil that they use simmilar but different addictives, and addictieves in organic oil will attack the syn oil and destroy it faster and it works opposite too. Its like when doc puts B blood into A person, DEAD. The Syn blend can work both syn or organic, and can be easilly changed into anything.
BUT there is some exeptions, some addictives will be fine with foreighn oil, so you can switch between organic and syn oil right away, but you don't know which is which so I wouldn't take chanches.
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