AMSOIL has the storage capability for about 1,000,000 gallons of base stock.
All of the oils/gear lubes are blended there, using one of the most advanced blending systems in the country.
As previously noted, they purchase base stocks and additive packages from a number of suppliers (all of whom are eager to do business). As a matter of interest to some, every incoming shipment of base stock (usually rail car) or additives is quarantined until a sample has been run through the lab. And yes, tanker cars have been returned to sender (usually only happens once to a vendor).