There must be a reason that every single stage and remote television production generator: gas or diesel, from 25kw, to over 200kw uses Synthetic in the engine for the past 30+ years I've been around them. That includes a small fleet of EU2000 used for the cleanup lighting after the big guns are put to sleep. They are run hard, stopped hot, and generally abused. When these engines fail, not only do they lose the job, they may never be called again.
I consider anything in this class a portable, and its simply not that expensive to fill a little Honda when a quart is probably 3 oil changes.