do you have a stick or auto' either way there are overdrive options for both, the stick would be easier.
also rear gears and tire size will make a world of difference.
I have had many leaning towers and they were very tough, but not necessarily mileage conscious. How ever they are easily modified for both mileage and power.It really depends on the whole combo. Start with the tallest tire you can fit.
Look for tall rears gears, should be able get a complete rear cheap to slip under it.
do you know how to check your gears?
Remember any of these changes will affect your speedometer.