What about a 300 running on biodeisel ???
In that case a short glow will probably help a lot to get it fired up quickly, which saves the starter motor from needing turning too long. On a really cold day if you don't glow it, the battery may go flat before it fires up. WITH glow, it should fire up quickly no matter how cold it is.
BioDiesel is generally less easy to ignite from cold, but makes the engine run more smoothly, which you should notice.
Once the engine is running on BioDiesel, the emissions from the exhaust will be MUCH less, and you will smell the Bio quite easily.
CharlesY