It's certainly possible that being added to your girlfriend's policy could be cheaper. For instance, if you live with your girlfriend and she has an established policy (and a good driving record) she will likely have a better rate for having continuous insurance. Plus, you can possibly qualify for a multi-vehicle discount.
That being said, there are many different factors that go into calculating your rate. These can vary from one company to another. The Zebra
can quote you with several companies at once. You can also give us a call at 888-807-3823.
Below you'll find some information on what makes car insurance rates go up as well as some tips for saving.
Good luck and if you have any questions, don't hesitate to ask