Well, I'm not for putting additives into a rig.  Get AAA or towing on your insurance.  And drive the snot out of it.  Most of your drive is flat, so you should be fine.  Just remember when driving up long steep grades, to downshift out of O/D.  Your trans will love you more.  Anytime I start climbing a slight hill, I take my vans trans out of O/D, and into Drive.  It doesn't over work the trans, by shifting alot.