Red line MTL transmission fluid is a popular replacement for and improvement over GM Synchromesh® (#12345349) and Auto-Trak II® (#12378508) as it lacks the reactive sulfurs found in most GL-5 oils that cause damage. This Fluid also offers quicker shifts, perfect synchronizer coefficient of friction and eliminates notchy shifting, even when cold. This fluid will help high performance gear protection and longer synchro life. This fluid satisifies the gear oil viscosity requirements of 70W, 75W, 80W, and motor oil viscosities of SAE 30, 10W30, and 5W30. Recommended for GL-1, GL-3, and GL-4 applications, as well as where most special synchromesh fluids are specified.