Credit Score Versus Interest Rate

Question: How does having a cosigner on a car loan effect MY Credit Score?
I'm looking at getting a car loan. My Credit Score is excellent, but because I have a short history and have never made a "big purchase" I can only get rates that are higher than I want. If my dad were to cosign for me, I can get an interest rate of about 2 points lower, which would be great, except that I want this "big purchase" to help with my Credit Score for the future (in case I want to make another large buy). What will the difference be to my Credit Score if I take out the loan on my own, versus getting a cosigner?
Answer: Auto finance is what I do for a living and the answer is none.
Your score will be impacted by how the loan is paid back not weather you have a co-signer or not.
When people co-sign both people get the exact same affect on their credit either good or bad depending on how the loan is repaid. When a lender looks at their credit they either see a "C" for co-sigh or a "J" for joint no one knows who is the co-signer and who is the primary signer.
Credit Scores AND Financial Resources