Got back from a weekend trip and noticed the bright orange Prestone is looking more red than orange. Smells strange and a flashlight shows a film on the surface of the fill tank.

This is an 83 so without an oil cooler I'm left to think there's something more serious to spend time/money on. Van runs fine and cool (just below the LED, where it normally is). No leaks or excess preassure/overflow with the coolant. Yet. Oil is about .5 quart down after 2000mi (synthetic). Oil does not look milky or smell strange.

Can anyone offer up ideas besides a cracked head for this?

john