Plastic plate covering the diesel tank fell off

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Do you only go to your dealer when there is a warranty problem, or do they do all the servicing also?

I know you didn't ask me but, I never went to the dealer (Solitaire Automotive) for servicing and they fixed many things under the warranty in our cars, with the courtesy car waiting for me, even washed it and vacumed it. Some broken thinks were of the similar kind as the OP's fuel tank cover.