04 mazda 3 problem

[flako77]

I recently noticed a gas smell coming from the rear of car (outside only) especially when I filled it up...and also I noticed my mpgs going down, check underneath no gas leaks, any ideas what it might b

 

[concept]

Have you checked the gas cap gasket to make sure it isn't damaged?
Also, here are other possibilities:
Corrosion around the fuel sender unit access panel. See http://www.mazdas247.com/forum/showthread.php?123718385-Has-Anyone-Had-Their-Fuel-Pump-Cover-Leak

MAF wire harness connector wires: While engine is idling, move the connector wires around to see if the idle smoothness worsens.

 

[kms1990]

charcoal canister soaked (vapor canister) or vent or purge valve solenoids having an issue do you keep filling after the pump auto stops? if so that can cause issues if done too much