Okay, so I was wrong.  The extra ordinary mileage reported earlier 
was a tank filling problem...  Averaging all figures for some 400 miles 
logged in the last 2 days I get an even-steven 38 mpg, not bad but no 
51 mpg.  Excuse me while I go crawl in a hole.  For those new to the 
thread this had little to do with vans except for an ECU temp sender, 
the mileage is for my Camry.

(signature line deleted to preserve my last vestige of self-dignity)