We have a new 2013 Fleetwood Expedition. I thought the DEF tank was suppose to be 5 gallons. It read at the dash and the tank gauge half full. I added 2.5 gallons and it only came up to 3/4 full. ...
I can see it fine. But I'm not the best judge of the volume. Anyway, it was at half a tank and it took 5 gallons to read full on both gauges. I didn't try to fit in 3 more gallons. Just assumed it was full. And based on that I guess it's a 10 gallon tank.
It looks like the extra $50,000 dollars on the Fleetwood model gets you the larger 13 gallon tank, probably a tag axle too, plus a few extra niceties. :B