Last week I bought a 2005 colorado with 174000 miles on it. I check the oil the day I got it and the level was fine and I could tell the oil was changed not to long ago still look new. Today I took the oil cap off and there was thick milky looking crap. I kinda of freaked cause I never saw it before in my life. But I have been reading that this can happen with a car or truck that had sat unused for periods if time is this true? There are no signs of a head gasket blown no white smoke and antifreeze levels are good and no overheating. But I know that doesn't mean anything my main question is how to fix and what to look for if it is a major problem?