Which then makes Castrol Edge 5W-30 LL the best because it is $24.04 on Walmart.com. $4.91/quart every day, and NAPA hasn't had a sale on the Mobil 1 product for months. Which then makes Castrol Edge 5W-30 LL the best because it is $24.04 on Walmart.com. $4.91/quart every day, and NAPA hasn't had a sale on the Mobil 1 product for months.