Seems likely. But how?

I've been experiencing this since the tank was full several days ago up to now down to about half a tank.

This might sound crazy.... But I'm having some kind of weird feeling that this could somehow some way be transmission related.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"