LONG-TERM TEST REPORT: 2013 Volkswagen Passat TDI. “As temperatures dipped below zero in early January, some staffers wondered if our long-term 2013 Volkswagen Passat TDI would be crippled by the cold. But just as it bucks the notion that diesel power means smoky emissions and gutless performance, our Passat started reliably even as temperatures dropped below minus-10 degrees Fahrenheit.”