When cars were less aerodynamic it probably held more truth. Not so much any more. If there is any difference it would be minimal. Your AC will probably last longer if you don’t use it!
Is she a good wife? Do you want to keep her? Then stop nagging her about meaningless details like this. Save your energy for important issues.
If you don’t plan to keep her, if you’d rather run her off, then keep harassing her…and line up a good lawyer…you’ll need one.