In my opinion the most important thing you can do to extend the life of your favorite Rig is to use synthetic lubrication.  Now days there is a lot of variety's to choose from, but the brand that has set the standard since 1972 is Amsoil. Amsoil Synthetic motor oils dramatically outperform conventional motor oils.  They reduce friction, heat and wear for maximum power, performance, longevity and fuel efficiency. I always try to encourage folks to go the whole 9 yards and change out all the fluids in their Rig.  Personally when I get real busy I tend to neglect a lot of the fluids, I feel that using the best lubricants available helps counter my neglect. Lets review a vehicles Fluids: - Engine Oil:  This is kind of a no brainier, but by using Amsoils high performance motor oils and their new Amsoil Ea oil filters you can run 25,000 miles or one year which ever comes first, don't that make life a whole lot easier.   While you are at it you might as well include a Amsoil Ea air filter, which needs cleaned after 25,000 miles but has a 100,000 mile life span. -Automatic Transmissions:  I am not a real fan of Auto trannys for off- roading but if you have one, like my wifes 454 Suburban has one, I highly recommend changing out the fluid and filter, Amsoil tranny fluid will run cooler and last up to three times longer.  Trannys are kind of a pain to change the fluid in and are often neglected.  Beware of Quick Lube flush systems, they may change all the fluid but leave the dirty filter in there, that is just  wrong.  Amsoils web site has explicit instructions on how to do both the right way. - Manual Tranny, Transfer case and Differentials:  This is a big time neglected area but if you fill them with Amsoil Severe Gear, basically, unless they begin to leak, you should never have to worry about them again. -Grease:  Time to grease all them Zert's and pack them Wheel Bearings, for 4X4ing I recommend Amsoils water resistant grease for when you get to splash threw a creek or you bury yourself in a Mud Hole it stays where it needs to be. If you haven't guessed I am an Independent Amsoil Dealer, I am really not going to give you a big sales pitch on becoming a Amsoil dealer yourself but there are some real good income opportunity's or even if you would like to buy the product at wholesale for yourself all I ask is that you would sign up under Me by using the ZO# of 1324650.  Then let me know by E- mailing me at clay@alpineparadise.com so I can offer my assistance any way I can. Amsoil has a very useful Aplication Guide on there Web site but if you have any questions or would like help specking out the types and amounts of fluids, types of filters etc, Please call me (Clay) at (970) 596-2158 or E-mail me at clay@alpineparadise.com. Let it be known that this advice is mine and not Amsoil's, please visit Amsoils web site to get there official advice.