Is oil conductive? Sometimes, actually

Is oil conductive? It’s a frequent point of debate among model railroaders. But generally speaking, oil isn’t a very good conductor. That said, oil can be a good conductivity enhancer, even though it’s not a very good conductor on its own.

Here’s how to use oil to improve conductivity in electrical applications. This can work whether you’re talking household current, or low-voltage applications like you find in model railroading.

Is oil conductive? Quantity matters

Is oil conductive? Sometimes.
Conventional wisdom tells us to keep this thing far away from electrical applications. But in small quantities, oil improves conductivity.

In large quantities, industry uses oil as an insulator. So that’s why it’s not a good idea to glom oil onto an electric motor or onto electrical contacts. In a large enough quantity, oil stops being helpful.

That said, I’ve brought dead electric motors back to life by putting one drop of oil on the commutator. And model railroaders frequently put a very thin coat of Wahl Clipper Oil on their track, or a specialty oil like Rail-Zip, to improve conductivity. The reason it ends up being such an intense debate is because it’s easy to use too much, and when you use too much, the oil becomes an insulator. So if you use the right amount, it solves your problem. If you use too much, you get two problems.

Why oil enhances conductivity

Oil in small quantities enhances conductivity for at least two reasons. One reason is that metal oxides are worse conductors than oil. Oil cleans off oxides and helps prevent new oxides from forming. So that dual effect can be very beneficial. I’ve taken to putting a very thin layer of grease or oil on the light bulb threads before I install a light bulb in a bathroom. It makes the light bulbs last a lot longer because it keeps the contacts on the bulbs and on the fixtures from getting oxidized.

The second reason it helps is because metal isn’t as smooth as it feels. Under a microscope you can see the metal still has pits and grooves in it that we can’t feel. Oil conducts electricity better than air, so a thin layer of oil can fill in those grooves, giving electrons more room to flow.

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