Probably teaching how to suck eggs but the reason for grease on stems and seatposts is to put a layer between the aluminium and steel since in contact they create a galvanic reaction which causes corrosion and leads to the stuck stem or seatpost scenario that most of us are unfortunately familiar with when renovating old bikes (although never with our own carefully maintained bikes of course). Copper and aluminium also create galvanic reactions together.
Steel on steel, no galvanic reaction but you just need something to keep the water out to prevent rust.
Ordinary grease will do both these jobs adequately on a bike.
Steel on steel, no galvanic reaction but you just need something to keep the water out to prevent rust.
Ordinary grease will do both these jobs adequately on a bike.