I was sitting in traffic today when I got a brief whiff of diesel fuel… Suddenly I was carried back thirty years to the farm where we lived for awhile when I was a small child. The great big barn behind our house was full of all kinds of cool old stuff, that little boys like to get into, like beat up old cars, machine parts, tools, farm stuff, and a general aroma of diesel fuel everywhere.
Another one: Mothballs. If I smell mothballs, I suddenly find myself in my first day at boot camp, trying on my brand spanking new uniform, still reeking of the mothballs they used to protect them in storage. Since my mom never used mothballs, I had never smelled them until I joined the Navy. Hence, the scent connection.