The 3 places dirt actually hides on your car
Most people wash the paint and call it done. That's not where the damage lives.
Wheel wells and the inner lip — road film cakes here and eats clear coat.
HVAC vents and seat tracks — that's the smell you can't quite place.
Door jambs and trunk seals — ignored until they stain the interior you just cleaned.
A real detail hits these, not just the hood. If your last wash still looks dull in a week, that's why.