Drive around town in "D" or "3" for MGP?

[Kar98]

Originally Posted by Shinare

I keep meaning to bring this up but always forget. I was told, by a car dealer, in reference to my A/T, that I should always drive around town in "3" and only ever use "D" for highway driving. He said this is the best way to conserve fuel and get the best MPG.

True or Myth?

Bullcrap. Put it in D.