FLUIDMATIC SYN T668 is a high-performance transmission fluid with extended oil-drain interval up to 150 000 miles under sever conditions or 300 000 miles under normal conditions, for specific conditions please refer to the Transmission Fluid/Filter Change Recommendations from Allison. Specifically developed for Allison very high-performance heavy-duty automatic gearboxes, FLUIDMATIC SYN T668 is approved by Allison TES 668.