"There aretwoprimary differences between synthetic oils and conventional petroleum oils. These are the base stock or liquid that makes up the volume of the oil, and the additive package. There are additives (not to be confused with over the counter additives which will be discussed later) in all oils that enhance the wear resistance properties of the oil, enhance the ability of the oil to neutralize acids and combustion by products, and provide corrosion protection for the engine’s internal surfaces. The amount and quality of these additives vary from one oil brand to another and this is a very significant factor in the ability of an oil to adequately protect your engine in all driving conditions. As a general rule of thumb, the cheaper the oil, the fewer additives it has and therefore, the less able it is to protect your engine.
There is one school of thought that suggests that the only difference in synthetic oils vs. petroleum oils is that the synthetics typically have a better additive package. This statement is only partially true. Synthetics almost always do have superior additives than petroleum oils. While this does add to the cost of the oil, it also enables the oil to last 3-5 times longer than conventional oil. The synthetic base stock however, is of paramount importance in the ability of a synthetic oil to flow at cold temperatures and withstand greater amounts of heat over significantly longer periods of time. Petroleum base stock molecules are long carbon chains that are sensitive to stress and heat. Additionally, various paraffins that are contained in all petroleum products regardless of how well refined they are, cause oil to jell like a syrup at extremely cold temperatures. At the other end of the temperature spectrum, high engine temperatures and heavy loads (as typically found in towing or racetrack applications) cause these chains to break down and the base stock actually boils off causing a change of viscosity and the formulation of sludge. This can happen at temperatures as low as 230º F and by 250º F many petroleum oils are suffering significant breakdown. Synthetic oils on the other hand are engineered specifically to provide all the lubricating properties that natural oil possesses, but none of the cold thickening or hot thinning properties of petroleum oil. Synthetics are made up of uniformly shaped molecules with shorter carbon chains which are much more resistant to heat and stress. Synthetics can withstand temperatures of 300ºF all day long and still protect your engine. In fact the American Society of Testing Materials (ASTM) standard wear resistance tests are conducted at 302º F. In this test synthetic lubricants far out perform petroleum lubricants by factor of four to one and greater.
Oil temperatures of 230ºF to 250ºF are not at all uncommon in driver’s education track conditions, particularly in early 911s with no front coolers or the marginally effective "trombone" oil coolers. These temperatures are also fairly common in air-cooled engines in summer time stop and go traffic with the A/C on. Further, temperatures on the cylinder walls and in turbos are often over 450
° F for short periods of time. Liquid cooled cars can also have extremely high oil temperatures even though the water temperature may be normal. I observed this first hand several years ago in a race car where the water temperature stayed right on 210ºF while the oil temperature fluctuated between 240º F and as high as 280º F depending on how hard the car was driven. Needless to say, this particular car was running synthetic oil and remarkably ran about 50 hrs. between rebuilds with no significant wear. Further, Winston Cup star Rusty Wallace was recently quoted after the 2000 twin 125 races in Daytona that his car was running a little hot with water temperature at 230
° and oil temperature at 260
° F. Rusty’s team is sponsored by Mobil 1 and I would think it is safe to say that they use the product.
The point of the above paragraphs is quite simply that synthetic oils have a much wider operating temperature range, by design, than petroleum oils. ... ...
Economics of Synthetics vs. Petroleum Lubricants
All of the manufacturers of synthetic oil tout the benefits of reduced wear, more horsepower, lower operating temperatures, and improved fuel mileage. All of these benefits are derivatives of better cold flow characteristics and higher levels of friction reducing additives that are found in synthetic oils. I can confirm better cold driving characteristics, increased fuel mileage of nearly 10%, noticeably lower operating temperatures, better heat dissipation capability, and long term high temperature stability based on my own experience with synthetic lubricants. Are these benefits enough, however, to persuade average drivers to give up their trusted petroleum oils and pay the extra price for synthetics? Enthusiasts, yes. Average drivers, perhaps not. However, synthetic lubricants can endure
extended drain intervals, which is a major consideration toward justification of the higher costs. This benefit is not widely promoted by the major oil producers most likely because they want you to pay a premium for their synthetic oils every 3000 miles just like their regular oils. Most companies don’t bother to tell you that synthetic oils are capable of going 25,000 miles or more without significant breakdown. One customer told me he drove his Toyota more than 50000 miles (with filter changes every 10000 miles) before oil analysis results told him it was time for a change. It is not uncommon for over the road truckers to go several hundred thousand miles between synthetic oil changes but it should also be noted that most are equipped with finer oil filtration devices than most passenger cars. The short trips and stop and go city driving that most of do is much tougher on motor oil than over the road highway driving. In fact, frequent short trips (2 miles or less) and stop and go city driving is considered by some raters as extreme and our cars need increased protection. Fortunately, we can achieve the superior protection and the economic benefits of synthetic oils while staying within the recommendations of our car manufacturers.
Consider the following economic argument. If you change your oil every 3000 miles at a quick lube center at an average price of $23.00 per change, you spend $115.00 over 15000 miles. Most synthetic oil changes cost about $50.00 (much less if you do it yourself) on which you can drive 7500 miles very safely (a 7500 mile interval is within virtually all manufacturers recommendations). Over the same 15000 miles, only two oil changes are required for an investment of $100.00. A shop could charge up to $57.50 and it is still a break-even proposition, plus you put a superior product in your car and are receiving the additional benefits that synthetic lubricants can provide. I typically drive about 12000 miles between changes with a filter change and oil analysis at 6000. Even after 12000 miles oil analysis advises that the oil is "suitable for continued use" and typically the wear metals are less than conventional oil after 3000 miles. In fact in a test performed by Popular Mechanics some years ago, oil analysis showed in New York City taxicabs that there is typically less oil breakdown and less wear metals in Amsoil 10W40 synthetic oil after 60000 miles (albeit with filter changes every 6000 miles) vs. conventional 10W40 oil after 3000 miles. As an added benefit, less waste oil is being put back into the environment. A true win-win proposition."
^ Link:
http://www.firstfives.org/faq/oil/oilartcl.html
"Synthetic oils, pioneered in the '70s by Mobil and now available from most major oil companies, take the all-season, multiviscosity approach to the outer limits. Unlike traditional mineral oils that are produced by distillation and further refining of existing crude oil stock, synthetic lubricants are made through chemical reactions. These new oils aren't synthetic or artificial in the sense that they're manufactured out of whole cloth--they still have the same natural ingredients found in "real" oil. But in a synthetic lubricant, these ingredients are recombined like a Lego set to yield synthesized-hydrocarbon molecular chains with desirable characteristics and uniformity not found in even the highest-quality traditional motor oils. Typically, the best synthetic oils use a combination of up to three different synthetic base fluids--polyalphaolefin (PAO), synthetic esters, and alkylated aromatics.
Because a synthetic oil's molecules are much more consistent in size and shape, they are better able to withstand extreme engine temperatures. By contrast, the unstable molecules in conventional oil can easily vaporize or oxidize in extreme heat. Mobil 1 synthetic is said to be
capable of protecting engines "at well over 400 degrees F"; in the real world, most racers have no problem running synthetics up to 290 degrees F under prolonged use, but they get really jumpy when a conventional exceeds 270 degrees F.
Because a synthetic oil is chemically produced, there are no contaminants in the oil. By contrast, conventional oils contain small amounts of sulfur, wax, and asphaltic material that can promote detonation as well as varnish and sludge buildup. With no wax, synthetics will flow at much lower temperatures than conventional oils. In fact, synthetic oils are now available with viscosity ratings as low as 0W-30, as in Mobil 1's new Tri-Synthetic blend or Castrol Formula SLX. These oils flow more than seven times faster than a conventional 5W-30 motor oil during initial start-up, yet at normal operating temperatures act like a regular Grade 30 oil.
An 0W-30 synthetic oil is capable of pumping easily at -62 degrees F and flowing at even lower temperatures. Conventional oils are essentially frozen solid at that temperature, so there's simply no conventional equivalent to this new grade. There are 5W-30 conventional and synthetic oils, but even here, the synthetic has a real-world advantage: Mobil 1's 5W-30 will pump at -58-degrees F, compared to about -35-degrees F for a conventional oil.
But claims and talk are cheap, so
Car Craft had Westech Performance run some of the new Mobil 1 0W-30 in Ford's prototype 392 small-block stroker crate engine. The Mobil 1 was compared to the generic (and recommended for this engine) 20W-50 factory-fill conventional oil, as well as 10W-30 conventional oil. All tests began with the oil temperature stabilized at 210 degrees F. The engine ran from 3,300-6,200 rpm, and several runs were made for each oil to ensure repeatability.
In terms of peak numbers, we found that the engine gained nearly 7 hp with the thinner conventional oil, and was up nearly 10 hp with the synthetic. No peak torque gains were observed by changing from 20W-50 to 10W-30 conventional; however, the synthetic was up 15 lb-ft of torque at the peak. Looking at average numbers helps explain where the gains occurred--both the thinner conventional and synthetic oils broadened the torque and power bands overall, but the thin Mobil 1 showed the greatest improvement under 4,700 rpm, indicating that the thinner oil provides less initial drag for the engine to overcome.
However, thinner oil also translates to lower oil pressure: The 0W-30 oil developed 10 psi less than the baseline 20W-50. Only 46 psi was on tap at 6,200 rpm--kind of shaky as most gearheads like to see at least 10 psi per 1,000 rpm. Still, the engine ran OK, and the bearings looked fine on teardown, seemingly verifying synthetic manufacturers' claims that their products' greater shear strength more than makes up for lower viscosity. Is 10 hp and 15 lb-ft worth paying two to four times more for a quart of oil? Or the potential for extended engine life? You be the judge."
^ link:
http://www.carcraft.com/techarticles...ventional_oil/
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