I know this is an older post, but these questions seem to come up frequently. Doing a search takes me to results mainly saying this oil is made by Citgo. I have seen post where Rural King customer service has even suggested it is Citgo oil. I have been running the RK branded (when it was still being sold), Warren Lubrigold (when they were selling it) and the Harvest King for the last 4 years. The 1qt jugs of all of the above have (had) the "WU" Warren Unilube on them. This is not on the 5qt jugs, but I don't recall it ever being on them. It would seem unlikely that the 1qt are Warren and the 5qt Citgo. Wouldn't it? Pic below is 0W20 just purchased today. My partial 1 qt bottles of 5W20 and 5W30 also have the "WU" symbol.