How problematic is this, though? Don't different grades of oil have different sulfur contents? Do you need a special kind of oil? How much more will it cost to refine? Will existing refineries will able to do this, or will they have to retool their refineries? This sounds great, but the devil is in the details.
From the article we have this:
For now, the promising technology is limited to California because to work right, the engines require low-sulfur gasoline that is widely available only there.
Crude oil comes in many different qualities.
Oil from Venezula is very high in Sulfur.