If a scent that felt perfectly balanced in summer suddenly seems weaker or duller once the temperature drops, that is not your imagination, and it is not a defect in the product either. It is basic fragrance chemistry responding to cold.
Fragrance oils diffuse through evaporation, and evaporation slows down significantly in cold temperatures. In summer heat, a fragrance card releases scent more actively and, as a byproduct, faster. In winter cold, that same card releases scent more slowly, which can make it seem less noticeable, especially in the first few minutes after getting into a cold car before the heat has kicked in.
There is a flip side to this that is actually good news for longevity. Because cold slows evaporation, a fragrance card in winter often lasts closer to the longer end of its range, sometimes stretching past the usual timeline, since less of the fragrance oil is evaporating away on any given day compared to a hot summer stretch.
The perceived intensity issue has a simple fix, though. Once the heater is running and warming the cabin, fragrance diffusion picks back up along with the air temperature, which is why a car can feel like it wakes back up scent-wise about ten minutes into a cold drive, once the interior has actually warmed. If you are judging a scent's strength in the first thirty seconds of a freezing morning, you are testing it under the least favorable conditions possible.
Closed windows for longer stretches in winter, less airing out overall, can also mean other smells, wet boots, damp coats, road salt, are competing more directly with your fragrance than they would in a season where windows crack open more often. A Balanced or Bold intensity scent, rather than something more delicate, tends to hold its own better against that winter competition. SIX in particular, with its bolder floral and musk profile, tends to read as more present in cold weather conditions than lighter, more citrus-forward scents like FOUR.
None of this means winter is a bad season for a car fragrance. It just behaves differently, generally slower to diffuse, longer lasting overall, and worth judging after the heater has had a few minutes to work rather than in the first cold blast.