I use "Howes Lubricator" in both my F 250 & E 350, I guess at what is an ounce or two at each fill up. The E 350 gets 20 mpg with 2400 lbs in it, to about 23.5 empty as long as I stay under 65 mph.
P.S
on today's front page under News Items head lines
"Bolt Express introduces new cash advance program" the article doesen't tell or explain anything. I work for Bolt and have heard nothing about it. Anyone out here with knowledge of this program?