Locally, Auto Zone (aka VatoZone, AutoZoned, AutoStoned) sucks. Great place to buy oil, but sucks for quality parts. I don't want to replace an alternator every year (or less). Their hard parts are noted for their high failure rates - unless something has changed drastically as oof late!
NAPA has the parts, but they are expensive, usually do NOT provide discounts, and if you order a part from a warehouse that is not local, they charge you for the shipping! And if it's wrong, tough!
O'Reillys is great here! I've had very few parts go bad from there, or be defective from the box. They offer several discounts, also, and they don't hesitate to price-match.
CarQuest (aka CarGuess) sucks. I actually had a young countergirl ask "What's a carb float?" when I went to get a float for a Carter carb. No, thanks.
Advance is OK, but I really don't do enough business with them to judge good, bad, or fair.
I'll NEVER use a Pep Boys store for anything - ever! They are the worst of the worst, for a lot of reasons.
I really miss the local mom-n-pop auto parts store that was right down the street - this was up to around 1999. They simply lost the desire to compete against the big names, and closed shop. Shame, too. They were terrific folks to deal with, knew you by name, and generally had whatever you wanted right there!
