Drive 3, 2 and 1?

d4 allows your car to go into top gear. yeah d3 does waste gas, at highway speeds it keeps it in 3rd gear rather than letting your car shift into 4th. it shouldnt mess up your engine, just keeps it revving higher more wear from higher rpm. actually driving with it in d3 when it rains isnt such a great idea, more likely to hydroplane as the higher revs will put more power to the wheels causing you to be more likely to hydroplane. very rare to have to use d2 or d1. unless towing start out in d1 and manually shift through the gears but just putting into d4 will work anyway. use d2 to start out in the snow, starting in higher gear puts less power to drive wheels making it easier to start out without spinning out. then after you get going shift into drive 4.