Toyota Repair: 97 4runner fuel usage, mileage figures, better mileage

Question
I own 2 97 4runners, one is a 2 wheel drive with 15" wheels, the other is a 4x4 with 16" wheels, both have the 3.4 V6 engine. The 2 wheel drive has 110,000 miles while the other has 120,000 miles. both are maintained together, the 2 wheel drive is horrible on gas, the 4x4 is much better, what should be checked to bring fuel economy up to the level of the 4x4?

Answer
I don't think I can be of much help unless I can have some gas mileage figures for each vehicle and the method that was used to calculate the mileage, normally the 2WD version will have better mileage than the 4X4, so if I could have the information on how the mileage figures were aquired and the actual variation between the two I can be of more help.