When I bought the truck it had sat at a shop for about a year they had drained the fluids out, we put water in it I believe when I test drove it, then I was told the mechanic put anti freeze in it so it wouldn’t freeze when I purchased it and I know it’s supposed to take HOAT and I know it’s not green coolant in it but it’s like it doesn’t really have a color and tommorow it’s supposed to get down to 18 and I was thinking about draining the coolant tank and putting straight antifreeze in it to make the mixture more concentrated so it doesn’t freeze, hasn’t froze so far this year but idk if it’s been that cold.

I know people say if you put the wrong coolant in or mix them it’ll destroy the water pump and the heads/ head gaskets and I do not want to do that but I’d also rather not flush the entire system if not necessary so I’m not sure what my best option here is

 

Drain some into a clear glass jar, and see what color it is.

 

You don't know what's in it, so getting rid of it and putting in fresh coolant will be peace of mind. I use the Walmart supertech concentrate mixed with 1 gal of distilled water to yield 2 gal.

Front end lower than rear when draining and higher than rear when filling.

 

is there any inherent harm in mixing coolants besides the fact that I’ll need to change it completely sooner? I’m almost positive it’s not green coolant but I believe there are a couple different types of yellow and one of them belongs in the truck as it takes HOAT which is yellow I believe, but even then there are different types of yellow, but being that it’s raining like hell and Christmas Eve, I’d prefer to not have to flush the system today this weekend I can but tomorrow it’s supposed to get down to 18 degrees coldest it’s been all year and I don’t want to risk it freezing

 

Ok now I’m confused when I look up the coolant type on a part store website it says HOAT and OAT (dex cool) will work but that doesn’t sound right that either would work. And mixing these will turn my coolant into gel is what I’ve heard and their both yellow so I guess I’ll have to do a system flush in the rain today but then what do I put back in the truck I have a Haynes manual that says HOAT is probably right but every vehicle is different refer to owners manual and I don’t have one of those I’ve had people tell me it took green HOAT and OAT and at this point I’m not sure what to do I don’t want to kill my truck with coolant

 

It uses HOAT. that's straight from the manual.

 

It will likely use either, and work just fine. The trouble comes from mixing coolant types. That is just bad, and leads to major destruction, your wife leaving you, (and taking your dog) and the world ending. That's why I suggest looking at the color, that will tell ya what's in there now, and you can just top it off. Now, if you really want peace of mind, flush the system thoroughly, and then put in the right stuff. Call it a day.