I think that you are going to have to find a product that will dissolve the diesel fuel, and wash it off. I don't believe that diesel fuel will ever evaporate fully; rather it would thicken as the lighter componenets evaporate, leaving an oily and still-smelly residue.

I've been hesitant to suggest what I am about to, primarily due to the danger of fire and/or explosion. Unfortunately, the only things that I can think of that would dissolve diesel fuel are both flammable and not good for you: something akin to gasoline or petroleum naptha.

I never tried it for this purpose, but 3M makes a product called adhesive remover that is 100% naptha. Using enough of this (at about $6 a can) may just rinse off all the diesel fuel from your trunk liners (if it doesn't dissolve them) as well as removing any protective wax from the paint inside the trunk. Make sure you can leave the trunk open until you smell no trace of solvent.

I would read label directions carefully, and not attempt this in a garage, or near other people, sources of ignition, smokers, etc.

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Robert W. Roe
1984 300SD 165K miles