Most major oil companies have informed U.S. customers of finished lubricant products of price hikes in September. They say the increase is driven by escalations in base oil,additive and packaging material cost.Chevron,Exxon-Mobil,Shell,Valvoline and BP Castrol will be hiking prices on average six percent. So if you want to save some money head to Wal-Mart,Advance or Napa and stock up before next month.