Paying $2.79 a gallon is great. Aside from that, since switching to Opti-Lube's XPD diesel additive, I’ve noticed a slight increase in mpg’s so far. My first tank consisted solely of highway miles, but was pretty respectable to say the least for the old Ford. I got 17.4 going roughly 66-68 miles per hour down a 275-mile stretch of highway.
So far since switching to the rear tank, I went over 80 miles before the fuel needle dropped below the ¾-full line, which hasn’t happened for a very long time either (Well, since having smaller Michelins on the truck). More to come on this for sure…
P.S. - Diesel is $2.57/gallon at a station in Woodland Hills, CA today. If you're in the area, go on and getcha some! Here's the link:
http://www.losangelesgasprices.com/index.aspx?fuel=D