6 Quarts of Mobil 1 Extended Performance High Mileage Formula 5W-30 Motor Oil for $18.24

It may be some type of glitch, but currently Walmart.com has three 6 packs of 1 QT Extended Performance High Mileage for $7 less than the equivalent 5 QT. I saw it for the 5w30, 0w20 and 5w20 but there might be more I missed. Here are the links:
https://www.walmart.com/nco/6-pack-Mobil-1-Extended-Performance-High-Mileage-Formula-5W30-1-qt/390999858
https://www.walmart.com/nco/6-pack-Mobil-1-Extended-Performance-High-Mileage-Formula-0W20-1-qt/394959516
https://www.walmart.com/nco/6-pack-Mobil-1-Extended-Performance-High-Mileage-Formula-5W20-1-qt/553682539