I have been told that you can extend the life of the SLLC coolant by adding a coolant additive. Does anyone know if this is true, and if so what brand of additive is available?

 

JMHO but I would not add anything other than OEM Toyota coolant to my cooling system...lots of small passages in there. That is one very expensive motor (besides the radiator/water pump/heater core/etc) that could be potentially gunked up inside with a 3rd party non OEM additive. I think the SLLC is good for 60k so I will just have it flushed and refilled at that point. My 06 LS has 45k on it right now and the coolant still looks perfect.