I have bought a 2012 300 and every now and then have a diesel smell coming into the car which lasts for about 5 min then it clears this can happen at any time.Have had the car checked out and no leak can be found.any ideas
If it is infrequent then it may relate to DPF regeneration cycle. The temperature of the DPF goes way up to over 600°C so if there is any oil or fuel around it will smoke off as the temp rises. If there are no fuel pipe leaks then there may be an exhaust leak at some point in front of the DPF you will get burnt diesel smell and probably smoke out of the engine compartment. Its really difficult to spot. Have your mechanic check the exhaust joints for evidence of carbon (a leak).
Does the service history show any turbo or EGR or other work carried out?