2000 Ranger, need to increase MPG !!!!

6 cylinder, automatic
126k miles, still getting over 20 MPG.
Runs great.
Looking for ways to increase MPG.
I drive 100 miles a day and with the rising cost of fuel, I need to do something.
Is there a way to make it breathe easier? (is that a good option)
Are there safe additives to increage octane without doing harm.
I heard that changing the values on the chip can make a difference too.
Looking to learn before I do, and then weight options
I really don't want to go to a 4 banger, but in these trying times, something has to be done.
As always... Thanks for your help and insight.

20 mpg! I would kill for that...but gotta have those big tires :)

there are a few simple things to do....one of the easist is to get a simple computer to tune your engine for better fule economy, some things ive done...i drive a ford ranger with a 4cyl 2.9ltr dual ignition....ive opened my intiake with a k&n system....ive incresed HP and have a higher fule useage pushing top RPMs....however when im doing normal city driving i have a better economy... higher horsepower mean engine works less(using less fule) to do the same about of work..but if you are heavy on the gas your burn a lot more...avg 20 mpg after k&n 22 mpg...however i am heavy on my throtle

Other than driving a little slower and keeping light on the accelerator, They have done test on most the add on so called gas saving add ons. Nothing has really proven to save much gas after you make the initial investment. I can add a couple miles per gallon by being real careful how I drive and slowing down a little.

I assume you have your V6 tuned regulary, plugs maybe new ignition wires etc., but have you ever changed the oxygen sensor? When O2 sensors age they richen your mixture and this means you will burn more fuel unnecessarily. Over a 100K is a lot of miles if you have never changed it. I find that many people don't know how important it is to change the O2 sensor. It will pay for itself quickly with rising fuel costs. Hope this helps.