Tachometer needle not showing the correct rpms

I've searched in here and didn't find this prob. Got a '03 Envoy XL that has a tachometer with a mind of its own. Instead of pointing at "0", it points to about 5-o-clock. At highway speeds, it is at around 7-o-clock. It seems that it is slowly creeping counter-clockwise. I also don't believe that it swings through the proper range as the engine accelerates/decelerates (the rpm range is compressed compared to normal). I have no other instrument panel issues. Any thoughts?

More than likely it is the tach, check the ground terminals on the l/s of the engine block, for corrosion or looseness first. This assumes it is a 6cyl., that info was omitted.

Slight update on this:

I've noticed that the tach needle will stay in position even with the key off, meaning that wherever the needle is pointing at idle, that is where it stays after the engine is shut off. Does the needle stem need lube? And what kind of lube should I use?

No such thing as lubing, this is not how this is designed.

Any updates? I'm having the same problem with our '04. It is the inline 6.

At this time, it is actually showing the correct rpms, without any doing on my part. Perhaps the warm weather re-established good contact at the ground point? The wife drives it, so I rarely get to look at it...it got its first good washing a month ago after a whole fall, winter, and spring! Sorry I couldn't be of much help, but I will recheck the block ground just to be sure.