My 2002 Trailblazer LTZ is getting coolant in the oil. What causes this?

Head gasket blown, less likely cracked head or block

Just changed the oil yesterday never started it up and looked this morning and it was milky. I started it and sounded bad for a minute and then drove fine.

I just drove it to the shop a mile from the house, is it a costly fix?

Unfortunately, yes. Expensive. It will dirve OK until it overheats, but do not drive it anywhere else, to prevent further damage from improper lubrication in the rest of the engine. Sorry to bear bad news. $1500 minimum

Wait, hold on...you changed the oil but never started it? Did you put the oil in the right place????

Yes. Lol . It ran hot one day so we checked the antifreeze and notices it was empty! So we added antifreeze and checked it the next day and it was empty again. Never drove it again after it ran hot. Checked the oil and that where we found our antifreeze. So we changed the oil and it went there again. Today is the first day I drove it since it got hot and we noticed the problem last week.

I didn't mean to insult you Stephanie. But it has been known to happen. So back to my first answer.

No insult taken. I've been known to do some silly things. I let a man do anything under a hood bc I could prolly do something like that.

Could it be a cracked Cylinder?

Sounds like a blown head gasket or intake gasket. Since you have water in the oil, it is not safe to drive. You will cause further engine damage by driving it. Very unlikely it is a cracked head or block causing the issue. It is an expensive job to pay to have done, and quite difficult to do on your own as certain specs (torque yields, etc) are needed as well as several specialty tools.

Today I drove it a mile to shop. Just kinda curious as to what it could be. Truck still drives fine though.

Sorry, the battery in my wireless mouse went dead and had to search around for a battery. Anyway, Michael is right, a cracked cylinder is remotely possible, and cracked head and/or block also, unless you drove it overheated for a long period, which it seems you did not. As I said, that coolant in the crankcase will render the oil almost useless. Sure, it will drive fine, but not for long.

Be prepared to spend some money. again, sorry to be the bearer of that

I guess I will no the fate of this tomorrow.

I found it's possible in the front timing cover where the water pump meets there's a second gasket behind it which separates the oil and coolant zone this could be leaking on the inside of the crankcase and then you can not at the moment I have a blown head gaskets more or an engine destruction if it's driven more about to explore more and find a situation out I know it's nine years since the last question on this but I figured this might help somebody go drop your oil pressurize the system and see if you can see it you drop the oil pan you'll be over to see it clean and if it leaks from the front should be able to take it flashlight up into the time in section and see it leaking from the housing itself