For a car hanger you don't want it to be too big so it won't block your view.  About 50mm (roughly 2 inches) seems about right.  

Make a circle at 50mm.  Make another circle at 3mm.  Move the little circle to 3mm down from the top of the first circle and select the two circles and horizontal center them.  Select both circles and choose subtract.  Add another circle in a similar manner and put it at the bottom.  Subtract this circle as well.  Set the object to cut.

Create your words and pick your font.

I like the words to fill up the space.  Resize your words to close to fitting.  Unlock the dimensions of the words and adjust height and width to make sure that it all fits into your circle but takes up most of the space.  If your words are cursive make sure to Weld them so that the engraving is even.  Set the words to engrave.

Since this is going to hang we need to add a little above our charm to make it interesting.  I am going to use rings and extra pieces of acrylic but you could use string and beads instead if you would prefer.  If you are doing beads you can skip this step.

I decided after creating the first one that I wanted to add some extra pieces to the hanger.  If you are doing the same, make a new circle at 11mm and add two 1.5mm circles to the top and bottom like we did for the larger one.  Or, what I did was copy the large circle, shrink it, and add the two new circles on top and subtract.  Either method will work.

I left the masking paper on so painting would be easier.  Engrave and cut the main object.  After cutting do NOT move the outer frame.  Pull the ornament (use tape to grab it if needed), flip it over, and engrave the words on the back as well.  This way as it spins the words will be visible on both sides.

Clean it off with a cloth to remove extra dust and use a brush or a paint pen to fill in the letters.  I let it dry for just a minute and then removed the paper. Some vinyl weeding tools are very helpful to remove the tiny parts on the inside of the letters.

Clean up any extra paint.

Cut the two smaller circles out of a different color of wood or acrylic.  

I used my largest jump rings to connect the 3 circles and then used smaller jump rings on the top to make a longer hanging chain.  Either make this long enough to go around the car's mirror arm or add a piece of string to the top to tie it on with.

At the bottom, use a few jump rings to add a crystal light catcher.  I got mine from Amazon but lot's of places carry them and they are relatively inexpensive.

Hang it in your car!  Mine is absolutely a true story and I do wait until my gas light is on before filling up most of the time, haha.