Mineral oil in battery

[Bill S]

The Aug. of Family Motor Coach magazine there was a article about putting 4 oz of mineral oil in each battery cell. It is to extend the life of the battery. Anyone ever heard this one before?

[38Tudor]

That's a new one to me.
I wonder what's the science behind that.

[green50]

I've never heard of it, however I found this.

"Oddly enough I asked about putting Thermoil or mineral oil in my new Interstate house batteries today. The Interstate store owner said not to put anything in the batteries but distilled water. They used to sell a product similar to Thermoil to put in battery cells, but found it did no good."

[51 MERC-CT]

The only thing it is supposed to do is reduce the evaporation of water by covering it with oil (oil floats on water) resulting in less battery level checks.
4 oz. seems high, probably closer to 2 oz. but depends on size of cells.

[tubman]

Originally Posted by 51 MERC-CT

The only thing it is supposed to do is reduce the evaporation of water by covering it with oil (oil floats on water) resulting in less battery level checks.
4 oz. seems high, probably closer to 2 oz. but depends on size of cells.

Now that makes sense. We used to do it in our toilets when leaving for a long period of time for that very reason. 4 ounces does seem excessive; maybe they mean those big deep cycle batteries. Given the configuration of a regular car battery, a few drops should be sufficient. However, with today's sealed batteries, it' s probably moot.

[rotorwrench]

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If the cells would stay full, a little oil wouldn't hurt anything. If the cell loses water then the oil gets on the spongy lead plates and fouls them.