The turbocharger/direct fuel injection combo has emerged as automakers’ favored choice for producing powerful engines and meeting government fuel-economy requirements. The increased airflow turbos generate enables an engine to burn more fuel and produce more power, but this power comes at a cost. The tremendous heat and stress turbos create cause some oils to break down and form harmful bearing deposits through a process known as turbo coking. Over time, turbos can suffer reduced performance or fail altogether.
The GM Turbo Coking Test requires an oil to limit the temperature change within the turbocharger to 13 percent or less to pass the test. Signature Series limited the temperature increase to only 3.6 percent, controlling heat and proving it protects against deposits common to high-temperature engine environments.