Double Platinum Member - 100 or more posts
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Well, the influence of water is really big here. In fact, the change of the dielectric constant due to water in oil is several times higher then due to "insolubles" (polar components from oxidation/nitration) in the oil. To make things worse, different oils show different dielectric constants after having the same service interval. If you have many samples you get a really rough picture, but I wouldn't interpretate too much in this picture. There are better ways of doing oil analysis.  |
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| Posts: 190 | Location: Germany | Registered: Sun June 13 2004 |  |
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Double Platinum Member - 100 or more posts
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Although it IS quite useful in transformer oils, I am not comfortable using dielectric change to measure engine oil age.
At least to my mind, there are too many possible variables in play in engine oil...a relatively insignificant amount of water contamination, as mentioned above, is more or less equivalent in effect to a massive amount of wear metals or oxidation. Further, the depletion of addivitives, TBN drop, and numerous other properties are hard or impossible to extrapolate consistantly from dielectric.
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Double Platinum Member - 100 or more posts
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Some vehicle manufacturers are now including an Oil monitoring system to tell you when it is time to change your oil. It is interesting that GM is not using dielectric readings in their system and instead using engine performance data and time to calculate (guessing) the optimum oil change interval. I agree that in an engine environment there are too many things such as moisture and combustion by products that can effect dielectric readings to make it a reliable single factor to determine oil life. Ray Garvy of CSI has written a couple papers on oil dielectric properties that you may find interesting check out the following link if interested; http://www.compsys.com/drknow/aplpapr.nsf?OpenDatabase&Start=1&Count=50&Expand=8 |
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| Posts: 162 | Location: Midwest, USA | Registered: Tue April 13 2004 | |
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Bronze Member - 1 or more posts
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quote:
Originally posted by cccous:
In my last GM vehicle I had the oil monitoring system you are speaking about. To me this system was pretty much worthless. I think one of the major things the system was based on was the engines rpm's. Even on the highway I think the most number of miles reached before the light came on telling me to change the oil was around 2,200 miles. It has gone off in as little as 1,200 miles. My wifes car is the same way. Just for kicks I had the oil analyzed and just as I thought the oil really did not need to be changed. To me it seems the GM oil monitoring system is pretty unreliable. There are probably quite a few unneccesary oil changes taking place as a result of this system. Just my opinion though.....
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| Posts: 3 | Location: Koblenz Germany | Registered: Tue August 03 2004 | |
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Bronze Member - 1 or more posts
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quote:
Originally posted by topoel:
quote:
Originally posted by cccous:
In my last GM vehicle I had the oil monitoring system you are speaking about. To me this system was pretty much worthless. I think one of the major things the system was based on was the engines rpm's. Even on the highway I think the most number of miles reached before the light came on telling me to change the oil was around 2,200 miles. It has gone off in as little as 1,200 miles. My wifes car is the same way. Just for kicks I had the oil analyzed and just as I thought the oil really did not need to be changed. To me it seems the GM oil monitoring system is pretty unreliable. There are probably quite a few unneccesary oil changes taking place as a result of this system. Just my opinion though.....
I made a mistake therfore I lost my notice. In Europe the new vehicles are using the same monitoring system. They only count the rpm, miles, how often you change the gears. There is a little chip inside which only counts.If you check the oil after the period of oil change you will be very astonished, because the oil mostly is out of the tolerances the car manufacturers are telling you. We made a lot of tests with car lubricants and mainly the tolerances are lost. There is no accurate system to count the contamination online. We have a system to test the oil but not online. There are to many faults which can influence the oil: Temperature; diesel or gas; long distance drive or driving only downtown (water contamination) |
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| Posts: 3 | Location: Koblenz Germany | Registered: Tue August 03 2004 | |
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