alrighty...since I found this....
my van got 14 with oversized tires but the same setup as yours...the turbo got me 15mpg..she gets better with WVO and WMO...about 16...new IP and injectors will show the gains in a few weeks..
my rear tank is 23gal..front is 18..
WVO is easy...filter it to 5 microns thru filter bags...let it settle..dont suck the water into the tanks..(water at bottom)...I genneraly blend it 50% if its gonna be 40* or warmer at night...75% if its warmer than 60* outside..any colder than 40* and I would run a 2 tank system with a heater/exchanger for the WVO tank and run straignt diesel in the other..