Okay so I've got to change oil in both trackers.  In my tintop I'm beating around the bush about trying synthetic/premium fluid for the first time in my life.  I'm kinda old-school and always believed regular oil is best for older engines but with all I've heard about synthetics and modern fluid technology for the past couple years, (especially from Jluck) I'm second-guessing myself.  For the other tracker, I don't care much about the oil, I'm just going to change it with cheap oil so I can smog it and eventually sell it, probably. 
Before I change the oil, though, I'm thinking about running one of these cleaning agents through it first.  I've heard Seafoam does some awesome things, but the rest I seriously wonder about.  I just want to make sure it passes smog but I don't want to waste my time and money on some advertising gimmick on a "tune-up in a can." 
Anyone have suggestions?
Also wondering if this stuff is worthwhile running through my tintop once in awhile.

I've run Seafoam in my gas tank before but have not tried it in the oil. I do it once a year and it does seem to clean things out and run better afterwards. If you haven't been running synthetic oil in your rig, I wouldn't change to it unless you have a new motor. You will get leaks and we already have enough of those.   

I've seen Seafoam improve idle, power, mpg and pass smog on a bunch of cars including 3 miatas, Lexus RX300, 1 tracker, 1 sidekick, Lexus LS400, Toyota Tacoma.  Its a bit of a mystery amoung my friends how the vehicles I drive run/idle so well. Seafoam, new plugs, wires, distributer cap and rotor go a loooooong way.   

Well I didn't have time to do it today.  Might be later this week...I should shoot video of the smoke show and post it 

Seafoam is great to use prior to an oil change & tune up. It will break up and loosen residue and harmfull deposits. Changing to synthetic oil will not create oil leaks. Bad gaskets allow oil leaks. Possibly changing to a lighter weight synthetic instead of a heavier conventional oil ran previously in an older engine might result in some leaks....

Look at it this way.... if an oil change caused an oil leak you were due to change the gasket anyway....