Residential spinning roof vent repair?

I have 2 of the wind driven turbine attic ventilators on my roof. One of them does not spin as easily as the other. It needs a lot more wind to spin. I've tried going into the attic and spraying lubricant on it, with no luck. Should I just go ahead and get a new one, this one is only 2 yrs old. Any suggestions. Thanks in advance.