The system is pressurized...if your cap leaks, then you will have problems with gas spewing out of the cap (especially on hot days)!

But I am concerned about the amount you are losing! A cap leak would lose trace amounts...perhaps you have a leak elsewhere.

It doesn't take much fuel to create a lot of odor!

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car