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Originally Posted by Lubehead
The concept that changing oil early in an engine will do damage is foreign to me. Damage is being done to the environment, not the engine. However it must be said here that if the engine oil is not kept clean and proper storage and/or handling of the engine oil is not exercised, whyireef's point about damage is a valid one. Spectrometric analysis of engine oil and the interpretation of the results is left to professionals that understand the lubricant chemistry, the functions of various additives and any pecularities related to the specific application and its history.
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Lubehead: I agree with many of your points, it is a well written summary. One comment is that oil analysis is a vital part of a condition-based monitoring program, but its use in consumer vehicles is often flawed. Individuals often take one sample, and look at the wear metals thinking that they provide a commentary on the oil quality, when what they really provide info on is the component that is wearing. Trending results over time provides valuable guidance, while single samples provide next to none and are oversold by the consumer oil labs. If we look to TBN, TAN, infrared, water/glycol contamination, fuel dilution, kinematic viscosity, and ISO particle count, we can learn about the oil. Users often don't purchase those tests, however, and fall back to trace element results.
I wouldn't go so far as to say that changing oil early will do damage, but there are many studies that show improved oil performance with use. The additives stabilize (they are aggressive when the oil is new), and so on. The lubricity of the oil isn't the only factor at work here, however, and viscosity degradation could offset any benefits realized in this sense, but there is enough evidence to suggest that more measurable wear metals in the first portion of the oil's life are somewhat to be expected. Here is one study. I used to belong to the SAE, but let it lapse, so I can't get the full study. The abstract follows.
https://shop.sae.org/technical/papers/2007-01-4133
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Originally Posted by SAE Published Paper ref 2007-01-4133
Abstract:
Engine oils are subjected to a series of industry standard engine dynamometer tests to measure their wear protection capability, sludge and varnish formation tendencies, and fuel efficiency among several other performance attributes before they are approved for use in customer engines. However, these performance attributes are measured at the end of tests and therefore, do not provide any information on how the properties have changed during the tests. In one of our previous studies it was observed that engine oil samples collected from fleet vehicles after 12,000 mile drain interval showed 10-15% lower friction and more importantly, an order of magnitude lower wear rate than those of fresh oils. It was also observed that the composition of the tribochemical films formed was quite different on the surface tested with the drain oils from those formed with fresh oils. The objective of this investigation is to demonstrate how the friction and wear performance changed with oil drain intervals. A fleet of three vehicles was run in Las Vegas and oil samples were collected at various drain intervals from 3,000 miles to 15,000 miles. As in the previous study, the results showed that the aged engine oils provide lower friction and much improved wear protection capability. These improvements were observed as early as the 3,000 mile drain interval and continued to the 15,000 mile drain interval. The composition of tribochemical films formed on the surface with the 3,000 mile drain interval is similar to that formed with the 12,000 mile drain interval as seen before. These findings could be an enabler for achieving longer drain interval although several other factors must to be considered.
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Last edited by JCL; 08-14-2009 at 01:19 AM.
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