I have read somewhere this has to do with a clogged vent. I do not have my Haynes handy, but this is ONLY a problem when it's less than half full when I fill up (i.e., when vapors accumulate - I presume)

Also worse when warmer outside.

This is driving me nuts

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former: 83 300D, 97 C230, 93 400E

current: 08 C300 Luxury , 92 500SL