856 Mpg :)
Well since I've converted I've never done a long trip with my truck. Only really commute back and fourth to work.
I had some friends move down to Durham NC so thought I'd pay a visit. The wife and I drive down and back 856 miles all together and bought no fuel at all. Only really used maybe a gallon of diesel the whole trip. Used 50 gallons of WVO.
Everything worked great.