Aredwood: Just pay for the proper full synthetic oil. As alot of cars 2005+ need full synthetic due to having exhaust particulate filters. And / or exhaust gas recirculation. As cheap oils cause the engine to produce ash ect as small amounts of oil get burned as part of the engine operating. This blocks up the particulate filter, exhaust gas recirc system, and inlet manifold. If these parts need cleaning/ replacing it will be very expensive. A new particulate filter will easily cost over $1000 just for the part only. And lots of labour involved to remove , clean and reinstall the inlet manifold and EGR system. All for the sake of spending an extra $50 every 6 months or so. (Cost difference between full synthetic oil and cheap mineral oil). And you would probably recoup that $50 through better fuel economy anyway.
Are you referring to existing diesel engines? AFAIK gasoline particulate filters on direct injection engines is emerging tech not mainstream yet.