Driving my w200 from New Jersey to Arizona some time in June. My question is, what is my best chance to help my MPG pick up and help keep the rpm, and thereby engine usage, minimal. Currently I've got a 4bbl 318, NP435, NP203, 33x12.5x15 tires. I'm not positive but I'm pretty sure axle ratio is 4.11. I will be checking that out. What are some suggestions as far as helping this old 78 out on its journey cross country.