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Electrical properties of standard lubrication oil (SAE)

  1. May 17, 2017 #1
    What are the electrical properties of standard lubrication oil (Engine oil)? Where to find? Please give the sources. I have tried my best on the internet.
  2. jcsd
  3. May 17, 2017 #2


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  4. May 17, 2017 #3
    My guess is you will not find them, if a manufacturer adds a "spec" for conductivity then they have to monitor and maintain it. There may be some "rule of thumb" values out there, but once in an engine, break down and degradation, carbon, sludge, metal flakes - all bets are off.

    So this begs the question - why do you ask?
  5. May 17, 2017 #4
    Which electrical properties, and specifically, what manner of oil? "Engine oil" itself is overly broad (mineral oil? if synthetic, what type?).

    One way to approach this is to answer, "How are the electrical properties of oil tested?" A sampling ...

    ASTM D257 - 14
    Standard Test Methods for DC Resistance or Conductance of Insulating Materials

    ASTM D3487 - 16
    Standard Specification for Mineral Insulating Oil Used in Electrical Apparatus

    ASTM D1169 - 11
    Standard Test Method for Specific Resistance (Resistivity) of Electrical Insulating Liquids

    Another is to research existing oil applications in electrical apparatus. This write-up on oil conductivity in HVDC gear may help define your thoughts.
  6. May 18, 2017 #5
    Thank you for your reply. I have already checked that website. Since I am research scholar, I need data from trust ful source.
  7. May 18, 2017 #6
    I am developing MEMS oil condition monitoring sensor. As a first step, I decided to make viscosity sensor. The model I have made works only in the non-conductive fluids. If lubrication oil has significant conductivity, then the design has to be changed. So I am collecting all the information about lubrication oil.
  8. May 18, 2017 #7
    I need electrical and mechanical properties of below lubrication oil:
    Engine oil SAE 15W-40, SAE 10W-40, SAE 10W-60, SAE 5W-40, SAE 0W-30, SAE 30
  9. May 18, 2017 #8
    How much conductivity is too much?

    Have you tried contacting engine oil manufacturer engineering departments?
    I can't recall seeing conductivity listed in any lubrication oil product data sheets, but they almost always provide the basics (viscosity, density, flash point, pour point, volatility, etc.).
  10. May 18, 2017 #9


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    Mineral oils and most of the synthetic oils are good insulators .

    Their electrical properties are usually characterised by breakdown voltage and dielectric constant .
    Last edited: May 18, 2017
  11. May 18, 2017 #10
    OK - so high conductivity will cause the test you have now to have problems. Then you are concerned about worst case? I still doubt there would be any good data - since you need to consider USED oil. In the field there are too many variables, including when the owner changes the oil to a different brand or spec. Since this is mostly an academic pursuit, another approach would be to limit the study to a few brands / types - etc. Go to a local shop and get some samples of used oil that they know the brand of - for example a known, reliable customer.

    I would echo to reach out to the Manufacturers and ask about the worst case - I am sure they have some data, but like I said it is not part of their specification.

    Lastly - Engine oil is probably the last place I would expect a MEMS sensor to be effective in the real world. Engine oil "goes bad" in so many ways - moisture & coolant, sludge, metallic flakes, thermal breakdown, even fuel, or customer added additives. Look at the BASIC Engine Oil analysis, I can not see the sensor surviving these variables, not to mention engine oil can routinely hit 125C most Silicon chips often max around 150C - and 125 is something of a design limit. . Sorry to be so negative.

    One approach would be to integrate the sensor into the oil filter, after the filter, so the sensor is changed with every oil change, and "sees' the cleanest oil having just been filtered.
  12. May 18, 2017 #11
    Add surviving a cold weather start-up to your list. I don't have in-depth experience with motor oil (unless you count doing my own oil changes), but in industrial gearbox applications, room temperature viscosity is significantly higher than when oil is at normal operating temperature. It is doubtful a MEMS turbine type viscometer would remain intact during the initial pressure surge (although this could be designed around by adding an isolation valve that opens up only after oil temperature has risen).

    Aside: While poking around the web, I learned late model BMW engines feature an oil condition sensor that measures temperature, level, and oil quality. Didn't find a detailed explanation of exactly how, but dielectric strength is measured as a proxy for oil quality. PDF file with sensor info. http://www.m3post.com/forums/attachment.php? s=ebb899a0ff1cdca95dd4c0ef202f8c0f&attachmentid=266653&d=1241794389
  13. May 18, 2017 #12
    My money is on an optical sensor looking at clarity.
  14. May 20, 2017 #13
    Used engine oil will be more conductive than new oil because it will contain particles of carbon and metal plus oil oxidation products. Conductivity will increase with age.
  15. May 22, 2017 #14
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