The purpose of the grease on the battery terminals is not to help conduct electricity, but to exclude air and moisture that assist battery corrosion.

Bob

... on the battery terminals! "Dielectric" means "doesn't pass electricity" so you shouldn't put the dielectric grease you use for spark plug wires on battery terminals -- you'd make your connection worse. High-voltage leakage is the problems on spark plug wires, and corrosion is the problem on battery terminals. There is anti-corrosion grease specifially made for battery terminals.

Guys,

I’ve seen several posts on the current board and others in the past and wanted to pass along some of my E28 under hood wisdom that comes with driving this car over 300K. Currently, on the board there are folks who get the radio pop when the brake lights come on.

Remove all the fuses from the box. Snug up the fasteners holding the box in place paying special attention to the hex-head fastener which plays a connectivity roll.

Every one of these cars that I see has plaque due to oxidation on the fuse connectors. Get out your Dremel (or similar weapon). With the small circular wire brush attachment, shine the fuse connections so the steel is gleaming bright. Check the fuses. Do they have plaque too? I’m not generally an advocate of replacing what’s not broken but the newer fuses are better and the handful you’ll need are only a few bucks. So in this case, I’d start fresh. Replace all fuses.

Touch every relay. Relays in the older cars have a tendency to ride out of their socket.
Make sure each one is seated properly.

Disconnect both battery terminals and remove the negative wire from its ground mount next to the battery. Using the Dremel again, shine up the insides of the battery connectors, the battery posts and the ground connectors. Lube the battery posts with a little of the lubricant used on spark plug wires and button everything back up.

Don’t be surprised if you notice some differences.

Merry Christmas and Happy Motoring