Well im new to TW and i have done counless hours of reading peoples mods and driving habbits to try and improve mpg. i have the 2.7 reg cab 4x4. and i am averaging about 32.4mpg. hwy. i have added an AFE pro dry cold air intake filter $240, doug thornley tri y header $407, a dynamax super turbo muffler, and have a Scan gauge II $200 mounted to my R/V mirror. all my fluids in my truck are full synthetic. (i like that phrase, think slippery) all u joints are lubed properly with that sweet and slippery moly grease. having such mods imporved my gas mileage from 25.6 hwy up to 28.7.. overall. about $1,250 worth of mods to increase horsepower significantly, (for better mpg while towing or carrying heavy loads) and up my mpg by 3.1mpg. worth the price? yeah, at about 90k miles it pays for itself at an average of $3.30 per gal.
the extra 3.7mpg i gain by a delicious thing i like to call high octane, ethanol free gas! there are few gas stations out there that offer such gasoline (here is a helpfull link http://pure-gas.org/) but really do the homework (may contain 10% ethanol) thats 2 gallons of ethanol in 20 gallons of fuel. leaving you with 18 true gallons of gasoline mixed with ethanol that honestly, your truck does not like. if you are running gas with ethanol the difference in high octane versus lower is minimal. but go for the ethanol free gas and the difference between low octane and 91 is quite noticeable. if you are skeptical, try it yourself.
4 cyl trucks dont run as smooth as 6 or 8's so being able to tell the difference with a 4 will be easier. your engine will run smoother and provide better horsepower with ethanol free gas. and most of all you are getting your extra 2 gallons of gas that you are paying for.