In any case, never, never, never give consent to search your vehicle. Think about it, are you 100% certain there isn't stuff in your car that could be used against you? Own a used car? Was it a drug dealer's ride? New car, it's been on test drives and many car lots let their sales agents take cars home with them.
A lot of the work that a criminal defense attorney has to do involves undoing the legal mess you created for yourself after the fact. You say yes to a search and they find something and now the search is legal. You say no and your attorney is successful, then anything found in that search might be suppressed as evidence.
Never say anything to a cop that you don't want repeated to 12 jurors. Do every legal thing in your power to prevent them from finding something that they can show those jurors.