My guess would be the filter might just be a little loose if there is fuel on top of it. There is a proper torque spec for it but I have found that I have had to exceed that in the past to get it to stop weeping past its seal. Try tightening the bolt a little and see if that stops it. Hold the filter to keep it from turning while you tighten it. Just do a little, maybe 1/16-1/8 turn.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz