I have put together some information about motor oil as a reference tool to assist and educate new and old members alike. I'm not pushing one type of oil over another, this is for education so you can decide what you want to use.
All information is taken from "The Motor Oil Bible". I greatly condensed the most important parts for easy reading (the full version is over 150 pages!), but I highly, highly suggest that you download the full version and read the whole thing.
Here's a link to it, Motor Oil Bible
There is much more
information than what is presented here, so it may leave you asking questions the the full version of The Motor Bible would answer.
The function of motor oil:
It must lubricate: Especially important at start up, oil must be quickly and easily pumped through the engine to provide adequate lubrication.
It must protect: A film forms in between moving parts to keep them from making contact is the obvious way it protects. But it also protects by providing corrosion resistance inside the engine. Oxidation of the oil and contamination via condensation and combustion by-products cause acids to form. Motor oil is made to combat these acids.
It must clean: Deposits that form in the engine reduces its running efficiency. An oils job is to keep these deposits from forming. Any particle larger than 5 to 20 microns can cause damage to an engine. Although filtration plays a big role in this, the oil has to play its parts by keeping deposits from forming and suspending them until they can be filtered out.
It must cool: Motor oil does the majority of cooling in your engine, the radiator does most of its cooling in the upper portion of the engine. The bottom end only relies on the oil to do its cooling. This is why the proper weight is important. Some think that if a 30 weight is good, then a 50 weight is better. Not so. If your vehicle was not designed to run 50 weight, then using a higher viscosity may not cause more wear, but will likely cause an increase in temperature, which is not desired.
How Petroleum oil is made:
Desalting - Aids in the refining process
Partial Vaporization - Separates the crude of different boiling points. The highest is used for basestocks
Vacuum Distillation - Separates the oil into different weights
Solvent Extraction - Up to 80% of containments are removed with this process
De-waxing - Wax is removed to aid in low temperature fluidity
Non Synthetic Synthetics:
There is a refining process called hydrocracking where a petroleum oil is refined on a molecular level to the point where it can be leagally sold as a synthetic. Though it is a high quality petroleum oil, it is still petroleum and not a true synthetic.
How Synthetic oil is made:
I can't really tell you how it is made since it is a chemical process. What I can tell you is that it is not refined like crude oil, but it is manufactured. It is pure with no contaminates and are made up of uniformly sized molecules.
Oil additives and their function:
Pour Point Depressants - Aids in low temperature fluidity
Viscosity Index Improvers - Aids oil to resist high temperature viscosity breakdown
Detergents and Dispersants - Cleans the engine and resists sludge buildup
Anti Foaming Agents - Self explanatory
Oxidation and Corrosion Inhibitors - Self explanatory
Anti Wear Agents - Minimizes wear if metal to metal contact occurs
Multi viscosities, the problems with them, and what the "w" stands for in 10w30:
Multi-viscosity oils such as 0w30, 5w30, 10w30, and so on are oils which are designed for applications where temperature changes may be significant. Most people believe that a 5w30 oil is good for cold weather use because it is a "5 weight" oil in cold temps and a "30 weight" oil at high temps. On the surface this might seem to make a certain amount of sense. Naturally, a "5 weight oil" would flow better than a "30 weight" oil.
The first number (the "5" in 5w30) is only a RELATIVE number which basically indicates how easily it will allow an engine to turn over at low temperatures. It is NOT a viscosity reference. Besides, if you thought about it for a second, it's not logical to think that an oil can be thinner when it is cold and thicker when it is hot. What liquid do you know of that thins out as it gets colder? Bet you can't come up with one. The fact of the matter is that the oil gets THICKER as the temperature drops. However a 5w30 oil will be less thick and flow better than a 10w30.
When the oil heats up to operating temperatures, all oils in the same weight classification, 0w30, 5w30, and 10w30 oils will perform the exactly the same because they are all 30 weight oils. Think of the "w"as a "winter" rating. Multi-viscosity oil provide a great deal more flexibility to protect an engine over a wider temperature range than monograde oils do.
Obviously, this should be considered a good thing. However, there is a drawback to multi-viscosity. When manufactured from a petroleum basestock, they tend to shear back easily. You see, the waxy contaminants within petroleum basestocks crystallize in cold temps causing them to thicken and become hard to pump. So, in order to allow for good flow characteristics at low temps a very thin basestock must be used in conjunction with pour point depressant additives.
For instance, let's look at a 5w30 oil. In order to flow well enough to meet the 5w classification, a super thin basestock is used such as a 20 weight oil. Then that basestock would be combined with pour point depressant additives. But in order to meet the 30 weight classification, the oil is "built up" using the long chain, high-molecular weight polymers called Viscosity Improvers. If you can already guess, as the oil ages, the Viscosity Improvers get used up and the oil shears itself back to its original 20 weight causing easier burn off leading to deposits, oil consumption and less protection.
The good news is, not all multi viscosity oils shear back so easily. Synthetic oils contain no waxy contaminants to cause crystallization and oil thickening at cold temperatures. This allows the basestock to be a true 30 weight oil with good cold weather characteristics. So, pour point depressants are unnecessary AND higher viscosity basestock fluids can be used which will still meet the "w" requirements for pump-ability.
The result is that very little shearing occurs within synthetic oils because they are not "propped up" with VI improvers. There simply is no place to shear back to. In fact, this is easy to prove by just comparing High Temperature/High Shear test results between petroleum and synthetic.
API testing and what they mean:
Kinematic Viscosity @ 40 degrees and 100 degrees C - Used for determining an oils viscosity
Viscosity Index - Refers to an oils ability to maintain a consistent viscosity over a wide temperature range. A good number to look for is 140
Cold Crank Simulator - An oil is cooled and a shaft is turned in it to measure the “startability” of the oil. The lower the score the better.
Mini Rotary Viscometer - A companion to the CCS test, this test measures pump-ability.
Borderline Pumping Temperature - The lowest temperature that an oil will adequately flow through your engine to provide the necessary lubrication and protection.
Flash Point - The temperature at which the oil vaporizes enough for the gas to become momentarily flammable in the presence of a small flame. Choose an oil with at least 420 degrees F rating.
Fire Point - The temperature at which the oil vaporizes enough for the gas to sustain a flame as opposed to a momentary one. Choose an oil with at least 450 degrees F rating.
Total Base Number (TBN) - This is a very important one here. This tells you the oils ability to combat corrosive conditions in the oil. The API minimum is 5, most petroleum oils are 5 to 8 and most synthetics are 8-14.
High Temperature / High Shear (HT/HS) - This simulates shear conditions in an engine. Different viscosities have different requirements. 30 weight oils has a minimum requirement of 2.9cP, so a higher number is better here.
NOACK Volatility Test - Also one of the more important test when choosing oil. The oil is heated to almost 500 degrees F for a period of one hour. The final score reflects the percentage of weight loss. The lower number the better. API maximum allowed evaporation percentage is 15%.4 Ball Wear Test – This method cover a procedure for making a preliminary evaluation of the anti-wear properties of fluid lubricants in sliding contact. Smaller the number the better. There are a couple of more, but these are the most common and most important. Download and read "The Motor Oil Bible" for the rest.
Why petroleum oil is inadequate:
PRONE TO BREAK DOWN:
Some of the chemicals in conventional petroleum lubricants break down at temperatures well within the normal operating temperature range of your engine. Others are prone to break down in these relatively mile temperatures only if oxygen is present. But, this is invariably the case anyway, especially since oxygen is one of the contaminants within petroleum basestocks.
When thermal or oxidative break down of petroleum oil occurs, it leaves engine components coated with varnish, deposits and sludge. in addition, the lubricant which is left is thick, hard to pump and maintains little heat transfer ability.
POOR COLD TEMPERATURE STARTS:
As caused by the waxes crystallizing in the oil.
MARGINAL HEAT CONTROL:
As the oil flows through your vehicles lubrication system, the small, light molecules tend to flow in the center of the oil stream while the large, heavy ones adhere to metal surfaces where they create a barrier against heat movement from the component to the oil stream. In effect, the large, heavy molecules work like a blanket around hot components.
Why synthetic oil is superior:
EXTENDED OIL DRAINS:
Synthetic oils are designed from pure, uniform synthetic basestocks, they contain no contaminants or unstable molecules which are prone to thermal and oxidative break down. Moreover, because of their uniform molecular structure, synthetic lubricants operate with less internal and external friction. The result is better heat control, and less heat means less stress on the lube.
HIGHER PERCENTAGE OF BASESTOCK:
Less additives are needed so you get a higher percentage of basestock
ADDITIVE USED UP MORE SLOWLY
Because you are starting with a more stable oil, the protecting additives in the oil are used more slowly.
EXCELLENT HEAT TOLERANCE
This goes back to the molecules in synthetic oil being uniform in size. An average Flash Point of several major brands of petroleum oil was 414 degrees F. An average Flash Point of several major brands of synthetic oil was 453 degrees F.
GREATER FILM STRENGTH:
Synthetic oils will typically have a film strength of 500% to 1000% higher than petroleum oils of comparable viscosity. In fact, believe it or not, even though heavier weight oils typically have higher film strength than lighter weight oils, a 0w30, or 5w30 synthetic oil will likely have a higher film strength then a 15w40 or 20w50 petroleum oil.
ENGINE DEPOSIT REDUCTION:
BETTER COLD TEMPERATURE FLUIDITY:
Question / Answer Section:
Q: Is there compatibility issues between petroleum and synthetic?
Q: When is too early to switch?
A: Unless the car came with synthetic from the factory, wait until 3,000 miles.
Q: When is too late to switch?
A: There isn't a definite answer to this, but generally over 10 years old and over 100,000 miles. Though many have successfully switched on cars with many more miles with no problems. A guess is that if 100 people switch their car over to synthetic and 5 people have leaks, where the other 95 do not, you are going to hear about the 5 people complain about it while the 95 successful people just go about their business
Q: Will oil pressure drop?
A: A small drop in oil pressure is typical because the oil is flowing easier. This is normal.
Q: Do I need special filtration?
A: You don't NEED special filtration, but a high efficiency filter is also as important as good oil.
My oil is dark, should I change it?
This is a huge misconception that needs to be addressed. The fact that your oil is dark does not in any way mean your oil is ready for a change. A large percentage of the contaminants in your oil is 1 micron or smaller. Only particles 5 and up cause damage. The smaller ones are safely suspended in the oil. A diesel trucks oil turns black in the first few hours of operation, yet the oil is used for many thousands of miles. Only an oil analysis can tell you weather or not your oil is still good or if it needs to be changed. * It is important to note that this applies more to synthetic oil. I personally wouldn't run a petroleum oil over 3,000 miles or 3 months because of the breakdown properties.
Mobil 1 oils are likely to go 10,000 or 6 months though they make no mention as to how long it can really go, and I doubt there is much difference between their regular synthetic and there new extended drain oils they are marketing. Amsoil makes a 7,500 or 6 month oil, as well as a 25,000 or 1 year oil that is guaranteed.
There is SOOOO much more information in "The Motor Oil Bible" It touches the subject of air filtration, oil filtration, and bypass oil filtration that I am not including here. It also talks about motor oil for motorcycles. Again, it is worth the time to download and read.
Modified by Buzzbomb at 9:20 AM 2/21/2006
Modified by Buzzbomb at 1:04 PM 2/21/2006
Modified by Buzzbomb at 2:19 PM 2/21/2006
Modified by Buzzbomb at 6:00 AM 5/9/2008
Modified by Buzzbomb at 6:02 AM 5/9/2008