aftermarket cooler has old thermal grease on it, bought a new CPU. is it ok if i pair it with the new CPU?

[ZachTNG]

Just bought an Intel i5-8600k, I have an aftermarket cooler with about 2 year old thermal grease on it. Would it be fine if I pair the both of them since I don't have any thermal paste with me right now. Or should I just go and buy another set of thermal paste?

 

[USAFRet]

Just bought an Intel i5-8600k, I have an aftermarket cooler with about 2 year old thermal grease on it. Would it be fine if I pair the both of them since I don't have any thermal paste with me right now. Or should I just go and buy another set of thermal paste?

That old gunk needs to be cleaned off and new paste applied.