have recently purchased an extremely well maintained Prochem Apex in a 2014 Ford E350, 21000 miles on van, 1100 Hrs in unit. After a long and sordid affair, getting the truck from Chicago to Canada and then waiting 4.5 weeks for a pulse hose, we were finally able to put the truck into service. Much to my shagrin the van has deplorable gas mileage, not while the unit is running but while driving. 3.5 Hrs running, under 60 kms driving, 1/2 tank of gas.....!! Any ideas??