1984 Z31 na almost 90k miles. A few nights ago, after sitting out for about 13 hours in 20 degree or slightly colder weather, my tach was acting a bit weird. I revved to about 2.5k and the tach stayed there for a few seconds and then began to slowly drop, even though I could hear the engine going to idle when I took my foot off the gas. As the car warmed up over the next few miles it started acting more normal again, its about a 10 mile drive home. No problems since. I always park it in the garage, except its now my daily driver, so its spending a lot more time outside. Is there a way to clean or lube the tach to help in the winter season, or is this even worth worrying about ?