Hey @user1235 ,
Have you checked the mesh quality, the warning suggests that there a few non-orthogonal cells:
You can use mesh quality tools to check where that is and add appropriate refinements. Overall though, convergence residuals look good enough to provide decent results. It is difficult to say what could have changed by not looking at your other cars. Please share the links to your other models with a different drag coefficient value for one of us to comment on possible reasons for deviation.
Also, double check the reference values you have used for this specific model and take a look at this article for different reasons why your values would not close to what you expect: Why Are My Lift And Drag Coefficients Too Big/Small? | SimScale
Let us know how it goes!
Best,
Satvik