Hello there!
 

Hi guys. I recently joined this forum with the hope of looking for information for increasing gas mileage on my truck. I have a 93 Ford Ranger with a 4.0. Would it be possible to squeeze 20mpg out of it? It already has a manual and is 2wd. I am already getting 18mpg. Is 2mpg hard to squeeze out of a truck?

yah, probably with technique alone you could do that. Wouldn't hurt to pump up the tires either.
Here are some rangers in the garage sorted by mpg:
EcoModder Fleet list - EcoModder.com

My Project Car is a 97 Mazda Protoge. But I also have a 94 Toyota PU. I would like to turn that into a project vehicle as well but .... one thing at a time.
For a truck (after reading on this site for the last year) low hanging fruit are:
1) Remove belt driven fan replace with thermostate controlled electric fan. (Only run a fan when needed to cool radiator --- don't run when not needed.)
2) Air dam. Underside of truck is aero dirty. Get more air going around truck not under.
3) Partial grill block. Most trucks have big flat fronts. Again only let as little air as needed into engine compartment get the rest of the air around/over.
4) Aero bed cover. Lots of good threads here on people who built bed covers.
5) If you don't use truck for hauling then see about lowering. Helps with item 2 and lowers frontal area.
But the number one thing is hypermilling driving techniques. With a few driving changes you should get 15-25% improvement (put you up around 21-23mpg)

Welcome. Let us know your successes and any test results. We all learn from each other.

Welcome to the forum! Agreeing with the others, driving technique is a great way to improve fuel economy. Gentle acceleration, plenty of following distance when you can (helps avoid constantly hitting brakes), time traffic lights so you avoid stopping as often and slow that vehicle down :-) With a stick, it is easy to kick it out of gear on gentle downhill grades and coast. Lots of great advice on this site if you're willing to try.