I own a 2001 330i, and am looking at replacing the battery on it, what do you suggest?

dealer battery, the battery has to be properly vented. remember it is located in the trunk.

Try Wal-Mart or Costco. Make sure you get the correct battery type. If they don't have it, try Interstate - they are better, but cost more. Autozone sells Exide batteries (same as Wal-Mart, but with a different label), but they charge more than Wal-Mart. Autozone also has more sizes, so you may need to go there.

You can go to the dealer, but be prepared to pay a lot for the battery. I had a new battery put in my Boxster (under warranty) and the dealer billed Porsche $350. I think your BMW will run $200-250 at the dealer.

I believe there are three of four major battery manufacturers left. Each has a slightly different look and they are all built different. The Interstate battery is the best, but they cost more.

Good luck!

Greg