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I need a rather large volume of oil to insulate a few 15 kV wires/coils. Unfortunately, the volume of oil required puts transformer oil outside of my price range.

I've noticed that others have discussed motor oil as a fairly economical substitute that works effectively around this range.

Are there any types of motor oils and/or materials inside of mineral oil that i should be taking into account when selecting a brand of motor oil?

As some background, the materials I'm insulating are made of copper with a few jagged edges. There're also a few little electrolytic caps and inductors.

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    \$\begingroup\$ So buy 1 litre cans of possible oils and run a few tests across the temperature range you expect. \$\endgroup\$ – Solar Mike Jan 14 at 22:19
  • \$\begingroup\$ Will EDM oil work, and if so, would it be any less expensive? \$\endgroup\$ – Scott Seidman Jan 14 at 22:34
  • \$\begingroup\$ @ScottSeidman Thank you for your advice, I'll certainly look into it a bit more. My main goal is to find something either locally (at a store) or relatively cheaply off of eBay. \$\endgroup\$ – Joshua Guertler Jan 14 at 23:54
  • \$\begingroup\$ You might try straight mineral oil. No additives as far as I know. \$\endgroup\$ – Robert Endl Jan 15 at 0:17
  • \$\begingroup\$ @RobertEndl I've checked out a few places, however it's almost all food-grade, meaning that they don't care if it comes in contact with water. Do you know of any places that might be able to provide straight up mineral oil that has been kept pure? \$\endgroup\$ – Joshua Guertler Jan 15 at 0:20
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Not too good because:

  1. Viscosity of motor oil is higher than transformer oil - so there will be risk of having some unfilled areas (filled by air).
  2. Motor oils can have some less or more conductive add-ons, like graphite, chemical compounds of lithium, molybdenum and so on.

Better choice is using liquid paraffin.

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  • \$\begingroup\$ Thank you for the advice. Since most manufacturers of non-electrical fluids will likely not regard moisture to the highest degree, I have a few concerns with selecting a liquid paraffin source that will fit the zero water tolerance of high voltage applications. Do you know of a place where I could find some? Most results give me paraffin lamp fuel (kerosene, effectively). While cheap, it would certainly make for an interesting display of reactions. \$\endgroup\$ – Joshua Guertler Jan 14 at 23:53
  • \$\begingroup\$ You can buy a liquid paraffin in pharmacy - it will be cleaner than paraffin for lamp ;) \$\endgroup\$ – VillageTech Jan 14 at 23:59
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    \$\begingroup\$ Density? Or viscosity? \$\endgroup\$ – DKNguyen Jan 15 at 4:28
  • \$\begingroup\$ You are right, viscosity is better word. Sorry, english is not my native language, and sometimes finding the best word is simply hard. I updated my answer. \$\endgroup\$ – VillageTech Jan 15 at 4:34

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