What to do about “Check gas cap” problem. 2004 Cadillac DeVille, 50,000 miles.
Make sure you tighten the cap enough (at least 3 clicks) after filling. If that doesn’t solve it, you might need a new gas cap. Another thing you could try is a little petroleum jelly on the gasket to see if that makes it pliable enough to create a good seal again.
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