So once again: if it involves a lot of moving parts (eg. tank tracks) you’d use a non-animated model with animated shaders. (You apply the shader just like any other, but the shader is responsible for making the textures animate.)
If there is simple movement (eg. truck wheels) you’d just seperate the wheels from the body and put those which are on the same axis (front wheels/back wheels) into one model.
To make them move, you first need a tag in the body so the wheels model’s origin can be attached to the body using scripting. After that, the script can rotate the wheels model just like it pleases.
Short: whilst modeling, you don’t need to animate anything if it can be done using scripting or texturing. The only thing you want to animate are complex movements. That way, you can save quite some filesize from the model since the model saves the positions of the vertexes in each frame.