Too much grease on the seat post? Seat turns
 

After reading last month's Bicycling Magazine about stuck seat posts, I regularly grease up my seat post so I avoid a freezing it.

However, I've noticed that my seat turns (while I am on it using my legs to turn) after using a bit of force. I've tighten the seat bolt as far as it goes and the seat post still turns.

Am I using too much grease?

No chance. You have some other problem. The seatpost may be the wrong size, the contact surfaces may be polished up too much, or the bolt may be stripped.
I'd think about wether you have the wrong size seatpost first.

Is your seatpost laprade or pillar?

Good call, operator.

It is a pillar seat.

I took a look at it again, and used my hands to twist by the seat. The post is definitely moving.

Not a carbon post right**********????

You say you are greasing it regularly since you read an article last month. How many times have you greased it? A light coat of grease once a year is enough unless you ride in lots of rain, muck, etc.

Take it out, thoroughly clean the old grease off the post and inside the frame with a degreaser, make sure it's perfectly dry, then put Tacx Carbon Assembly Compound on it and tighten to specification with a torque wrench. It will no longer slip, yet it will not get stuck. You should use the Tacx compound whether its carbon or not; that doesn't matter. There are some other equivalents to the Tacx compound as well from other manufacturers (it's likely all the same stuff) but it's specifically designed for greasing clamped parts.

Use the Tacx like pmt says. . . good stuff.