I have a '98 6CYL SR5 w/ 242,000 18 mpg
and a 2004 V8 15 mpg. The towing for the 98 is good for a small cart trailer but if you are going to tow 4000 lbs every weekend, buy the V8 if you can find one. Under no circumstances should you buy a 2wd. You will forever be kicking yourself!
