How does adding a co-signer affect the loan

[RussianPassion]

After quick credit repair project (from mid 500 to low 700 in 4 months) I am not ready to get an auto loan. I have no doubt that I will get approved. My question is this... I want to add my wife who has a horrible credit (due to her being young, naive and silly) as a co-signer for a sole purpose of jump starting her credit. Would that affect the loan? How do they treat a co-signer? Will the interest rate get diluted based on her bad credit and end up being higher than if it was just me? Would the banks be hesitant to give me credit due to my bad credit co-signer?

[Creditaddict]

Most banks that I have worked with lately for auto loans, take the highest score out of the 2 of you and put that person as primary and then factors in income and debts for both of you... unless she is totally out of wack for debt vs income, you should probably be able to do it without to much concern.