in town?
In normal city driving, where you would never get above 45mph, your 4-speed automatic will probably never shift into 4th. So there would be no difference between having the shifter in "3" or "D".
But if your town is hilly, and you have a few long hills that you normally drive 45ish down, keeping it in "3" will insure you have some engine breaking. If the auto shifts into 4th going down long hills you'll put more wear on your breaks slowing it down.
I suspect Nissan wants you in "D" normally so that there will never be a case where you rev 3rd gear too high. I drive in "D", except in snow or other slick conditions. My town is hilly.
OpalBlue
In normal city driving, where you would never get above 45mph, your 4-speed automatic will probably never shift into 4th. So there would be no difference between having the shifter in "3" or "D".
But if your town is hilly, and you have a few long hills that you normally drive 45ish down, keeping it in "3" will insure you have some engine breaking. If the auto shifts into 4th going down long hills you'll put more wear on your breaks slowing it down.
I suspect Nissan wants you in "D" normally so that there will never be a case where you rev 3rd gear too high. I drive in "D", except in snow or other slick conditions. My town is hilly.
OpalBlue