Ridiculously long internet search shows only cars approved on the 228.31 spec (bevo), vans may use 228.3, 228.5, 228.51 or 229.3, 229.31, 229.5, 229.51, 229.52. So my guess is they don't consider 228.31 a truck oil for whatever reason. That's all that's available in the common parts stores that...