Motor Oil Change -
How Often, What Kind |
What is the best oil to use in my engine and how long can I go
between oil changes? How do I judge the trade off between a high price oil with
longer interval with lower price oil and more frequent oil changes?
These are questions people face, especially when they have a special car or plan to keep the car for a long while. I hope to shed some light on the subject, but not make your decision for you. I am not a salesman, nor owner of a lubricating oil related business. I am an engineer who spent many years on the oil industry and also a car enthusiest. I enjoy my old Corvettes and am presently looking for a 56 or 57 Corvette if anyone knows of one. The question is often phrased: Do I spend more for a synthetic oil or spend less and get a "regular" oil? What is the difference?. The real question is not how oil performs in laboratory test, but in your engine. That will vary, depending on condition of the engine and driving style. Do you drive mostly at steady highway speed or a lot of stop and go? Engine oil operates in a hostile environment. It is normally 200 to 300 degrees Fahrenheit, pumped under pressure, then released to be splashed on crankshaft and rods that are moving very fast. This causes oil to foam, increasing contact surface of oil droplets to combustion products; an atmosphere not un-similar to a refinery where it was produced; an atmosphere well suited to chemical change. So, the question can only be answered by testing the oil from your engine after it has run the desired number of miles. The test can be done for about $50, providing you with a list of contaminants in your oil, including particles that are small enough to get through the oil filter, but still cause wear. Regular oil is made in a refinery from crude oil by a chemical process involving separating different components of crude oil, then selecting and recombining some components into a product that meets specific goals of lubricating properties. [Oil is a mixture of products!] There are National Standards that define properties of lubricating oils and all major brands meet or exceed those properties. Any of these oils will do a good job protecting your engine with regular maintenance. That is, change oil and filter regularly. I prefer to change this oil every 2000 to 2500 miles. Synthetic oil is manufactured by a different method. Where regular oil is a mixture of multiple compounds, synthetic is mostly one component that is designed to meet lubricating properties. Different manufacturers include special additives and make special claims for them. Claims it is slicker; claims that you can wait longer between oil changes, up to 7500 miles. I am including portions of a post by Hib Halverson to a Corvette interest group on the Internet. It started as a discussion/argument about the relative merits of two synthetic oils and claims made by companies. Hib describes some standard laboratory tests for lubricating properties of oil. You can have these tests performed on any oil, both new and used. The same general discussion applies to any oil. The argument about the tradeoff of many miles (more than 5000) between changes and low miles (2500) usually involves claims that a particular oil will "last longer". If you pull the dipstick from most engines with even 10,000 miles on the oil, the oil will still feel slippery. It "can" still lubricate. The reason for the quote marks is, the oil is usually not the problem; it is other things in the oil. While running, an internal combustion engine always has some leakage past the piston rings. That is; unburned fuel as well as combustion products get past the rings into the oil. Unburned fuel can wash oil from the cylinder walls causing wear. Wear produces metal particles in the oil. Your oil filter will trap particles over a certain size, but smaller particles will pass through the filter and circulate through the engine, causing wear on bearings, rings and cylinder walls. The combustion products include many compounds, including acids that will both combine with and break down engine oil. Synthetic oil will resist breakdown better than regular oil but carry particles just as well. Additives to any oil are also subject to chemical change due to combustion products that can reduce their effectiveness and may even make them harmful. An oil filter will not remove liquid chemicals that result from combustion. The following is somewhat technical, but can be informative. I have a few more comments after Hib’s. by Hib Halverson Independent Oil Test Results; Which Oil Really is Best? Four Ball Wear Test, (ASTM D 4172) (60 kg pressure @ 150 deg. C, 1800 rpm for 1 hour duration) "In the Four Ball Wear Test, the smaller the wear scar, the better the protection. Tests conducted by an **independent lab**, (the Falex Corporation), show that AMSOIL series 2000 20W-50 Synthetic Oil provides up to four times more protection than other popular synthetic and conventional oils." Ok, VNers, we went through all this last Spring when we got the Amsoil flim-flam the first time. I think what I should just do is say, simply that: The four-ball test is irrelevant when you consider what goes on with oil inside an actual working engine. This is why Amsoil relies on the four-ball test to try to get you to buy their multi-level marketed product rather than testing the stuff in a running engine. In a real-world situation, like...inside the engine of your Corvette, Red Line is clearly superior. I've been looking around for test data to support that belief. Interestingly, I got my first lead right off the back of an Amsoil bottle. Recently, Amsoil introduced a new race oil with considerable advertising. An aggressive marketing strategy published ASTM D 4172 antiwear test data on each container of oil. This data compared Amsoil to Red Line oil and other industry leaders. I imagine the Red Line people were flattered that Amsoil chose it as a benchmark in synthetic lubrication. Let's take a sec and talk about the test itself. It is American Standard Test Method (ATSM) # D 4172-82 and is known to lab types as the "four-ball" test. It is a very common test used to quantify the ability of a lubricant to lubricate. Specifically, it is used to determine the relative wear-preventative properties of lubricating fluids under prescribed test conditions. Three 12.7mm (0.5-in) steel balls (AISI standard E- 52100 steel, 64-66 Rockwell-C) are clamped together and covered with the lubricant to be evaluated. A fourth 12.7mm steel ball, called the "top ball," is pressed into the cavity formed by the first three balls with a force of either 147 or 392 Newtons (15 or 40 Kg). The temperature of the lubricant is regulated to 75 deg. C (167 deg F) while the top ball is rotated at 1200 rpm for one hour. Lubricants are compared by using the average size of the scar diameters on the lower three balls. The test can be run under different force, rpm and time parameters, which as you will see, Amsoil and Red Line chose to do. More detailed information is available in ATSM publications that one can find in a good technical library. On examining the data printed on the Amsoil bottle, I noted, expectedly, that the testing, which Amsoil commissioned and funded, showed Amsoil as being superior to Red Line. I became suspicious, when I read closer then realized how large a "margin of superiority" Amsoil was trying to convince me existed. Remember....buyer beware. Red Line Synthetic Oil Corporation was also very interested in Amsoil's claims...to the point of running their own battery of tests. First, the obvious: Red Line bought some of the new Amsoil Series 2000 race oil and had it tested according to the ASTM D 4172 Wear Test under the same parameters Amsoil used. Red Line found that unused Amsoil tested as advertised. Next, Red Line departed from the test conditions a bit. They actually tried Amsoil in an engine. Whoa...an amazing concept, eh? Red Line filled the crankcase of a 4.0L V6 engine in a Ford Aerostar van and began driving. They took samples at 338 miles and 919 miles. These samples were compared to those of unused Red Line 20W50 and Red Line 20W50 taken from the same Ford V6 operating under the same conditions as the Amsoil Series 2000 was run, except for one thing....the Red Line 20W50 was run for twenty times the Amsoil mileage, *twenty-thousand miles*. RL 20W50 was also tested after 2252 miles in a 2.0L Turbo in a Saab and RL 40 Wt. race oil was tested after 1300 miles of drag racing and street use in an LT5 out of a ZR-1 that is, coincidentally, by a subscriber to the ZR-1 List. The results of these tests were just what I expected. While Amsoil might be good stuff coming right out of a bottle; after it's been run in an engine for relatively short periods, it clearly falls short of a lubricant that I would put in my Corvettes or, for that matter, the engines in my other two "beater" cars. As a manufacturer of high-performance synthetic lubricants interested in making oils that enhance the durability of engines that use them, Red Line does a great deal of testing of antiwear additives, friction reducers and synthetic base oils. There are many components which it could add to its products to make them perform better in ASTM tests on unused oils. However, their goal is selecting a specific oil chemistry that adequately protects a running engine not simply obtaining good test numbers for advertising and marketing purposes. Red Line had some samples of fresh Amsoil Series 2000 analyzed. Based on that data, they told me they believe some of Amsoil 2000's components are highly chemically reactive, which could allow the oil to react with steel very aggressively in the new oil test and get good numbers. However, when exposed to blowby gases in an operating engine; they think these additives deactivate rapidly, bringing the wear characteristics right back to what you would find with any synthetic oil. A unique characteristic of Red Line synthetic engine oils is that, tested in the same manner, their wear numbers actually *improve* with use. No surprise there. Part of Red Line's synthetic additive package and base oils react with the blowby gases to create a more effective antiwear chemistry. That is clearly proven by the ASTM D 4172 Wear Test of used RL 20W50 run out to several different mileages. The necessary tests are not expensive. An ASTM D 4172 costs about $45.00. An independent laboratory that can perform that test at reasonable cost is: Petro-Lubricant Test Labs, Inc., 170 N. Main Street, Bldg. 2, Wharton, NJ 07885 (201) 366-3797. Another lab that does that kind of testing at a slightly higher cost is: Falex Corporation, 2055 Comprehensive Drive, Aurora, IL 60505 (708) 851-7660. The objective of ASTM tests are to make the results independent of the laboratory, so use any testing laboratory you choose. Either lab requires only 3 ounces of oil to perform the tests. Specify ASTM D 4172 with 60 Kg and 1800 rpm at 150xC for 1 hour which is the test specified in the Amsoil literature. In each case, keep a sample of each for yourself. If you suspect the numbers are erroneous, you can retest with another lab. This is Verle again: For my part, while Synthetic is often "slicker" and resists breakdown better, I use regular oil and change oil and filter frequently so I can get the contaminants out of the engine. The best oil and best filter will still not remove all the particles and none of the liquid contaminants. If you are making only long, constant highway speed trips, you can get by with a longer interval, in town, stop and go traffic, change it more often. If you want to know what brand is best... The answer is similar to religion; what were you brought up with?
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