The overflow always looked fine but tonite I decided to check the coolant level in the rad itself.
And under the cap there was no coolant that I could see..

No biggie I thought I just top it off with distilled water.
But it turns out it took half a gallon!

I never had issues even in traffic jams in this hot summer heat AC blasting..
Just bought the truck 7 months ago never had cause to heck under the rad cap always just looked at the overflow and it seemed fine.
Comments/Thoughts ?