I went to change my heater hoses today because one of them blew a leak , but anyways I went to my local NAPA to get the hoses and some new antifreeze. They had two different types of antifreeze: A gallon of havoline extended life collant for $25, or SEIRRA coolant for $8. So being the cheapskate that I am, I get the seirra, thinking it was the same stuff. But I get home and read the label and find out that seirra is different, it is made from propylene glycol, instead of ethylene(sp?) glycol like most antifreezes. So my question is, is it bad to mix the two? because I already have some of the other in my car.

 

I dont know for sure if it's bad or not, but I wouldnt do it. Drain it, flush it and use ONE type of coolant. Less headaches you know ?

 

if you haven't opened it just return it and get some plain jane ethylene glycol for $6. I think the exteneded life stuff you saw is mandaded for new GM cars, "Dex-Cool", that's why it's an arm and a leg. The Sierra is propylene cuz it's less toxic.