Change my oil every 4,500-5,000 miles and average 32ish mpg. Might want to redo your math.
Prime example of why not to listen to this synthetic shenanigans. Anyone who pushes that much and takes that much time to explain it more than likely has something to gain. Never take advise from someone who will gain from it.
Oh and this cost crap. Local shop charges $30 for dino change $90 for synthetic change. So synthetic cost 3 times as much at that shop and I can go 3 times the miles but synthetic will save me money? Makes perfect sense!