Engine Oil Dielectric

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.

Cccous,

A comparision with values for Transformer oil is interesting.
Transformer oils are basically straight minerial napthenic type of oils and are Superclean as well (NAS 7). They are theoritically speaking a special type of "Heat transfer oils" as thier function is primarily to cool the transformer. During operation of a transformer oil it is rarely oxidised, and have an infinite life. They fail, when moisture or dirt levels increase.

Transformer oils are rejected if its die-electric constant exceeds 0.005. In most case dehydration & filteration of these oils rejunevates it and oil can be put back to use. This value can thus be taken as a reference for other oils as well.

Hussam Adeni

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.

Abus
IF you look at the majority of the oil quality sensors out their the majority are of a dielectric based sensor. I believe that you are correct in saying that contamination of the oil will indeed affect the dieelctric reading. However, is this really a bad thing?? It would seem to me that one would like to know if the oil was being contaminated by water and or metal debris. IF indeed the oil was being contaminated by one of the above mentioned items I would think that the dielectric reading would change so much that you could use this reading to determine that something is wrong. I would think that using the dielectric to measure both the life and contamination of the oil would be a good cheap method.

Hussam Adeni
Seeing as since the transformer oil is a super clean type oil, can it be compared to engine oil??? From the sounds of it the transformer oil needs to be "super clean" to perform well. Based on the dieelctric change of .005 it does not seem that the two can be compared and stated to be similiar. As state earlier from an earlier experiment I noticed a difference of anywhere from .2 to .4 from the clean reading to the dirty reading( manufacturerers recommended oil change). Any input??

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

Yes I agree with you, transformer oils cannot be compared to Enginine oils. The objective is to use it as a reference "good condition" which should translate to no/low moisture or contamination.

Hussam Adeni

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.....

Thanks for the links to Ray Garvy's papers. Looks like it could be some very intersting stuff!!!

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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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Originally posted by topoel:

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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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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)