TLDR version: After 30 days, RockAuto's mistakes become your problem.
Been a member since 2009, and somehow this is my first post! Generally don't say much unless I think it would help others. A recent mistake cost me about $200, hope to help others avoid that:
Looks like lots of others here also purchase from RockAuto. Have had great luck with them, and you can't argue with their prices. EXCEPT: on my last (very large) order they sent me some incorrect parts - a control arm and two front rotors were wrong, even though the catalog listed them as correct. It was a big project, and I was outside the 30-day return window before I was able to get to the project (finally had a local shop do it).
Here's the rub: they refused to refund them, even though it was their mistake. I even offered to take a restocking fee. They suggested I should have checked them for fit right away (right, because it takes just a minute to check to see if a rotor fits the hub or control arm fits!). I sent multiple follow-up emails just to be sure they understood the situation. Got 3 different responses, all basically telling me to pound sand. Had to buy the correct ones locally, and have some expensive paper-weights as a result.
Something to keep in mind if you are ordering from RockAuto, and don't always have time to get right to work to see if they sent you the parts they told you were correct. I don't always have that time, so will be sourcing parts locally or from Amazon vendors in the future (Amazon policy forces vendors to correct mistakes on their end. Others may as well).
