I commute year round weather permitting (ie no snow temps>single digits) on 4 different older road bikes:

90' Raleigh Technium-Pro, with fenders and a rack,
87' Panasonic DX-4000 with fenders,
86' Vitus 979 no fenders,
and 94' RacingBik (aka Aegis) Carbon Fiber no fenders.

Normal route is 28 miles round trip and hilly longer route is 38 round trip. I usually have a backpack to carry the necessities.