1) Do you have any other installment loans?
If not- You pay the majority of the interest in the first years of your auto loan. As such, even if you had a 3 year 30k loan, you would only pay about 300 in interest the final 9 months. To me 300 bucks is worth 15 points on your FICO score when you apply for a mortgage - it will more than make up for it in the interest you save over the next few years on your mortgage.