ok so i was jus goin to the gas station today and my service engine light came on so i went to auto zone to have them read the codes for me. it said coolant temp regulation, well they told me that my coolant is low and need to refill it, so i bought a bottlwe ands refilled it, then they told me if its still on its my thermostat. well i turned it back on, waited a fewminuites lights still on, so i went to advanced auto parts and had them pull the codes for me. same code, coolant temp regulation. they told me that the mixture of the coolant isdifferent from what the truck calls for and i need to flush it and fill it again. and all this is doing causing the truck to take longer to warm up. someone tell me there theory, what should ido about all this? i just bought the truck a month ago at a dealership, its a 2001 4.3 sfi auto tranny. is it safe to drive. the temperatures been running fine. help me out guys.