Originally Posted by mkguitar
oil traps and holds dirt
clean and dry
I think the logic was that was a good thing, as the oil would make the dirt non conductive and also absorb the oil mist which was much worse on the old batteries. Similar to the other thing that is still done, which is totally covering the battery connections with grease.
Starting batteries these days are pretty much all calcium lead models and use very little water, so not really a problem under the hood anymore. Even the marine "deep cycle" Costco battery, gp 27, that I use for a starting battery in the van, doesn't use any water and never messes up the top of the battery like out coach deep cycle wet cells did.