Thought I'd throw in my recent fuel smell experience for posterity.
Never really noticed a smell during taxi, takeoff, climb out. One in cruise and leaning, would start to notice smell and it never cleared, just kept smelling for the duration of the flight.
I had an avionics project done (new panel, engine instruments and sensors, and Cies senders) not too long ago.
Initially though senders gasket leaking, but no blue, maybe gascolator, no blue. Never saw blue on the gear legs, wings, belly, anywhere I could see without unscrewing something.
Turns out it was the fuel pressure sensor fitting. (Opinion of the shop is that the avionics installer put an old fitting on the pressure sensor and never leak checked). Fuel was power washing the firewall... And right over the cabin air intake and exhaust.
Yikes!
I even had an oil change once in the meantime and the leak wasn't noticed by the shop that did the change.
Next time I smell fuel, I'm just going to land or go straight to the shop.